Sintering device, method for preparing solar cell and solar cell

Abstract

The invention provides a sintering device, a method for preparing a solar cell and the solar cell. The sintering device comprises a first heating area, the first heating area comprises a first conveying mesh belt, the first conveying mesh belt is provided with an upper portion and a lower portion, the upper surface of the upper portion is used for placing battery pieces, and the lower surface of the upper portion is in contact with a vibration generator. Therefore, in the heating process of the battery piece in the first heating area, the vibration generator can provide a vibration field with a certain frequency, so that the surface tension of slurry on the surface of the battery piece is reduced, the wettability is improved, the contact resistance of the slurry and a silicon wafer substrate is reduced, and the open-circuit voltage and the filling factor of the battery piece are further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a sintering device, a method for preparing a solar cell and a solar cell. BACKGROUND

[0002] In a crystalline silicon cell structure, a silver grid line is laid on its upper surface to collect photo-generated current, and an aluminum back field is laid on its lower surface to block the movement of electrons, reduce the recombination rate of back surface carriers, and increase the absorption of carriers (so that more carriers form current). In the sintering process, the silver grid line and the aluminum back field form good contact with the silicon substrate, which is a prerequisite for ensuring good conversion efficiency. In order to reduce the reflection of light on the crystalline silicon cell and increase the light absorption rate, texturing treatment is often performed on the front surface to reduce light reflection, but the pyramidal texture structure can cause the silver grid line to not fully contact the silicon substrate, resulting in an increase in the contact resistance of the crystalline silicon cell and a decrease in the fill factor, thereby leading to a low conversion efficiency.

[0003] Currently, some researchers have differentiated the texturing of the grid line position and the non-grid line position on the front surface of the crystalline silicon by mask processing (preparing large texturing or a flat surface at the grid line position) to improve the contact between the silver grid line and the silicon substrate. Although this technical means can improve the contact resistance of the grid line, it requires additional manufacturing processes, increases production costs, and the growth and removal of the mask are difficult to control, so it is not suitable for industrial production. Therefore, it is necessary to explore and develop a low-cost technical means to improve the contact resistance of the grid line and / or the aluminum back field.

[0004] Therefore, the current sintering device, method for preparing a solar cell and solar cell still need to be improved. SUMMARY

[0005] The present application aims to at least partially alleviate or solve at least one of the above-mentioned problems.

[0006] In one aspect of the present application, a sintering device is provided. In some embodiments of the present application, the sintering device comprises a first heating zone, the first heating zone comprising a first conveying mesh belt, the first conveying mesh belt having an upper part and a lower part, the upper surface of the upper part being used for placing a cell sheet, and the lower surface of the upper part being in contact with a vibration generator. In this way, during the heating process of the cell sheet in the first heating zone, the vibration generator can provide a vibration field with a certain frequency, so that the surface tension of the slurry on the surface of the cell sheet is reduced and the wettability is increased, thereby reducing the contact resistance between the slurry and the silicon substrate, and further improving the open circuit voltage and the fill factor of the cell sheet.

[0007] In some embodiments of the present application, the vibration frequency of the vibration generator is 10-1000 Hz. In this way, the vibration force provided by the vibration generator can effectively reduce the surface tension of the paste, so that the paste can fully contact the silicon wafer substrate, thereby reducing the contact resistance between the paste and the silicon wafer substrate.

[0008] In some embodiments of the present application, the sintering device further comprises a second heating zone and a cooling zone, and the second heating zone, the first heating zone and the cooling zone are arranged in sequence.

[0009] In some embodiments of the present application, the second heating zone comprises a second conveying mesh belt for conveying the battery sheet; and / or the cooling zone comprises a third conveying mesh belt for conveying the battery sheet. The plurality of conveying mesh belts divide the sintering device into a plurality of zones, and the battery sheet is first subjected to heating treatment in the second heating zone, then enters the first heating zone for heating treatment, and then is cooled in the cooling zone to complete the sintering treatment of the paste.

[0010] In another aspect of the present application, a method for preparing a solar cell is provided. In some embodiments of the present application, the method for preparing a solar cell comprises: providing a silicon wafer; forming a raw passivation layer on the back surface of the silicon wafer; treating the raw passivation layer by using a laser to remove part of the raw passivation layer and form a back passivation layer having a plurality of grooves; printing a paste on the front and back surfaces of the silicon wafer; and performing a sintering treatment on the silicon wafer printed with the paste, wherein the sintering treatment comprises a first heating treatment, and during the first heating treatment, the silicon wafer is placed above the upper portion of a first conveying mesh belt, the lower surface of the upper portion of the first conveying mesh belt is in contact with a vibration generator, and the vibration frequency of the vibration generator is 10-1000 Hz. In this way, by providing a vibration field with a certain frequency through the vibration generator, the surface tension of the paste on the surface of the silicon wafer can be reduced, the wettability of the molten paste to the silicon wafer substrate can be improved, the paste can fully contact the silicon wafer substrate, thereby improving the contact performance of the grid lines and / or the back field lines to the silicon wafer substrate, reducing the contact resistance, and further improving the photoelectric conversion efficiency of the solar cell.

[0011] In some embodiments of the present application, the first heating treatment comprises increasing the temperature from the first temperature to the second temperature at a first temperature increasing rate; and before the first heating treatment, the sintering treatment further comprises a second heating treatment on the silicon wafer, the second heating treatment comprises increasing the temperature to the first temperature at a second temperature increasing rate and holding the temperature, and the first temperature increasing rate is greater than the second temperature increasing rate. Increasing the temperature to the first temperature at a smaller temperature increasing rate and holding the temperature can remove the organic substances in the paste and can play a certain role in shaping; and then increasing the temperature rapidly at a larger temperature increasing rate can make the paste melt and sinter rapidly, so that the front grid lines and / or the back field lines obtained by sintering have a good morphology, and there is no "hollow" between the front grid lines and / or the back field lines and the silicon wafer substrate, the contact resistance between the front grid lines and / or the back field lines and the silicon wafer substrate is small, and the photoelectric conversion efficiency of the solar cell is high.

[0012] In some embodiments of the present application, the method satisfies at least one of the following conditions: the first temperature increasing rate is 15-25℃ / s; the first temperature is 390-410℃; the second temperature is 810-850℃; the second temperature increasing rate is 10-15℃ / s; and the holding time at the first temperature is 18-22s. In this way, the photoelectric conversion efficiency of the solar cell can be further improved.

[0013] In some embodiments of the present application, the back passivation layer has a plurality of groups of groove lines arranged at intervals, each group of groove lines corresponds to a back field line, and each group of groove lines comprises two or three groove columns. Forming a plurality of groups of groove lines on the back passivation layer, each group of groove lines is formed by irradiation of a smaller laser spot, and the smaller laser spot causes less damage to the back passivation layer, which is beneficial to improve the performance of the solar cell.

[0014] In some embodiments of the present application, the sintering treatment further comprises a cooling treatment after the first heating treatment.

[0015] In another aspect of the present application, a solar cell is provided. In some embodiments of the present application, the solar cell is prepared by the method described above. In this way, the front grid lines and / or the aluminum back field of the solar cell are in full contact with the silicon wafer substrate without "hollow", the contact resistance between the front grid lines and / or the aluminum back field and the silicon wafer substrate is small, and the solar cell has a high photoelectric conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the description of the embodiments, taken in conjunction with the following drawings in which:

[0017] Figure 1 A structural schematic diagram of a sintering device according to an embodiment of the present application is shown.

[0018] Figure 2 A structure diagram of a sintering device in the related art is shown;

[0019] Figure 3 A partial structure diagram of a silicon wafer after sintering in Comparative Example 1 is shown;

[0020] Figure 4 A partial structure diagram of a silicon wafer after sintering in Example 1 of the present application is shown;

[0021] Figure 5 A partial structure diagram of a silicon wafer after sintering in Comparative Example 1 is shown;

[0022] Figure 6 A partial structure diagram of a silicon wafer after sintering in Example 1 of the present application is shown;

[0023] Figure 7 A structure diagram of a back passivation layer according to one embodiment of the present application is shown;

[0024] Figure 8 A structure diagram of a back passivation layer according to another embodiment of the present application is shown;

[0025] Figure 9 A structure diagram of a back passivation layer according to yet another embodiment of the present application is shown;

[0026] Figure 10 A structure diagram of a solar cell according to one embodiment of the present application is shown;

[0027] Figure 11 A structure diagram of a solar cell according to another embodiment of the present application is shown.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] 100: first conveying mesh belt; 110: upper portion; 120: lower portion; 200: vibration generator; 300: second conveying mesh belt; 400: third conveying mesh belt; 10: silicon wafer; 11: textured surface; 20: front side grid line; 30: back side grid line; 40: back passivation layer; 41: groove; 42: first passivation layer; 43: second passivation layer; 1: conveying mesh belt; 2: cavity; 3: groove line; 3': groove column; A: first heating zone; B: second heating zone; C: cooling zone. DETAILED DESCRIPTION

[0030] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the same or like component have the same or similar designations. The embodiments described below are presented by way of example only and are not intended to limit the present application as defined by the appended claims.

[0031] In one aspect of the present application, a sintering device is provided. In some embodiments of the present application, referring to Figure 1 The sintering device can include a first heating zone A, which includes a first conveying mesh belt 100 having an upper portion 110 and a lower portion 120, an upper surface of the upper portion 110 being used for placing battery pieces, and a lower surface of the upper portion 110 being in contact with a vibration generator 200.

[0032] Referring to Figure 2 The sintering device in the related art uses one conveying mesh belt 1 to transport battery pieces, and no vibration force is introduced during the sintering process. In the present application, the first conveying mesh belt 100 is used to transport battery pieces in the first heating zone A, and the vibration generator 200 is introduced. During the heat treatment of the battery pieces in the first heating zone A, an external force can be applied by the vibration generator 200 to reduce the surface tension of the paste, increase the wetting performance of the front grid paste and / or the back aluminum paste, thereby improving the contact between the front grid lines and / or the aluminum back field lines and the silicon wafer substrate, reducing the contact resistance, and further improving the photoelectric conversion efficiency of the battery piece.

[0033] It should be noted that the lower surface of the upper portion 110 of the first conveying mesh belt 100 is in contact with the vibration generator 200, which can be achieved by directly contacting the lower surface of the upper portion 110 through the vibration generator 200, or indirectly contacting the lower surface of the upper portion 110 through the vibration generator 200, as long as the vibration generator can provide a low-frequency vibration force to the first conveying mesh belt.

[0034] In some embodiments of the present application, the vibration frequency of the vibration generator 200 can be 10-1000 Hz, for example, the vibration frequency of the vibration generator 200 can be 10 Hz, 50 Hz, 100 Hz, 300 Hz, 500 Hz, 800 Hz, 1000 Hz, etc. In this way, the vibration generator can provide a certain force to the first conveying mesh belt, effectively increasing the wetting performance of the paste, thereby improving the contact between the front grid lines and / or the aluminum back field lines and the silicon wafer substrate, and effectively reducing the contact resistance; the vibration frequency within the above range is beneficial to maintaining a good morphology of the front grid lines and / or the aluminum back field lines, and is not prone to collapse.

[0035] In some embodiments of the present application, referring to Figure 1The sintering device can further include a second heating zone B and a cooling zone C, and the second heating zone B, the first heating zone A and the cooling zone C are arranged in sequence. During the sintering process, the battery piece can first be subjected to heating treatment in the second heating zone B to remove the organic matter in the paste, and then the battery piece enters the first heating zone A for heating treatment and high-temperature melting. The low-frequency vibration field provided by the vibration generator 200 makes the paste better contact with the silicon wafer substrate under the action of external force, thereby reducing the contact resistance between the front grid line and / or the aluminum back field line and the silicon wafer substrate, and further improving the reliability and photoelectric conversion efficiency of the battery piece.

[0036] In some embodiments of the present application, with reference to Figure 1 The second heating zone B can include a second conveying mesh belt 300 for conveying the battery piece. The heating area is divided into the first heating zone A and the second heating zone B by using the first conveying mesh belt 100 and the second conveying mesh belt 300. During the heating process of the battery piece, the battery piece can be conveyed in different heating zones by different conveying mesh belts, which is convenient for operation, and the vibration generator can be added only in the first heating zone to improve the wettability of the paste and improve the contact between the paste and the silicon wafer substrate.

[0037] In some embodiments of the present application, with reference to Figure 1 The cooling zone C can include a third conveying mesh belt 400 for conveying the battery piece. The battery piece is conveyed in the first heating zone and the cooling zone by different conveying mesh belts, which is convenient for the transmission of the battery piece in different areas, and the vibration generator can be added only in the first heating zone to provide vibration force, avoiding the adverse effect of vibration on the cooling process.

[0038] In some embodiments of the present application, with reference to Figure 1 The second heating zone B can include a second conveying mesh belt 300, and the cooling zone C can include a third conveying mesh belt 400. The three different zones convey the battery piece by different conveying mesh belts, which is convenient for operation.

[0039] In some embodiments of the present application, the first conveying mesh belt 100, the second conveying mesh belt 300 and the third conveying mesh belt 400 can convey the battery piece under the driving of the respective rollers.

[0040] In some embodiments of the present application, the first heating zone A can further include a first heating assembly for heating the battery piece to melt the paste on the surface of the battery piece. In some specific embodiments of the present application, the first heating assembly can include resistance wires and / or infrared heating sources.

[0041] In some embodiments of the present application, the second heating zone B can further comprise a second heating assembly for heating the battery piece to remove organic matter in the paste on the surface of the battery piece. In some specific embodiments of the present application, the second heating assembly can comprise a resistance wire and / or an infrared heating source.

[0042] In some embodiments of the present application, the sintering device can further comprise a furnace body, and the first heating zone A, the second heating zone B and the cooling zone C are located in the furnace body.

[0043] In another aspect of the present application, the present application provides a method for preparing a solar cell. In some embodiments of the present application, the method for preparing a solar cell can comprise the following steps:

[0044] S100: providing a silicon wafer.

[0045] For a PERC (Passivated Emitter back contact) cell, the silicon wafer can be a P-type silicon wafer, and before forming a passivation layer, the silicon wafer can be textured to form a textured surface on the surface of the silicon wafer, and then phosphorus diffusion (to form an N-type doped layer), PSG (phosphor silicon glass) removal, alkali etching and annealing can be performed.

[0046] S200: forming an original passivation layer on the back surface of the silicon wafer.

[0047] In some embodiments of the present application, forming an original passivation layer on the back surface of the silicon wafer can comprise the steps of forming an aluminum oxide layer and a silicon nitride layer, and the silicon nitride layer is located on the side of the aluminum oxide layer away from the silicon wafer. For the method of forming the original passivation layer, the present application does not make specific limitations, and those skilled in the art can select and set according to the actual situation, for example, the PECVD (plasma enhanced chemical vapor deposition) method can be used to form the aluminum oxide layer and the silicon nitride layer.

[0048] S300: treating the original passivation layer by laser.

[0049] After forming the original passivation layer, the original passivation layer is treated by laser to remove part of the original passivation layer and expose part of the surface of the silicon wafer, thereby forming a back passivation layer having a plurality of grooves.

[0050] S400: printing paste on the front and back surfaces of the silicon wafer.

[0051] In some embodiments of the present application, aluminum paste can be printed on the back surface first, and then dried, and then silver paste can be printed on the front surface of the silicon wafer and dried. For the specific composition of the silver paste and the aluminum paste, the present application does not make special limitations, and those skilled in the art can select and set according to the actual needs.

[0052] S500: performing a sintering treatment on the silicon wafer on which the paste is printed.

[0053] In some embodiments of the present application, the sintering treatment can include a first heating treatment, during which the silicon wafer is placed above the upper portion 110 of the first conveying mesh belt 100, the lower surface of the upper portion 110 of the first conveying mesh belt 100 being in contact with the vibration generator 200, the vibration frequency of the vibration generator 200 being 10-1000 Hz, for example, the vibration frequency of the vibration generator 200 can be 10 Hz, 40 Hz, 80 Hz, 100 Hz, 200 Hz, 500 Hz, 700 Hz, 1000 Hz, etc. By providing an external force to the first conveying mesh belt through the vibration generator, the paste printed on the silicon wafer on the first conveying mesh belt is vibrated, the surface tension of the flowing paste is reduced, the wettability is improved, so that it can be more fully contacted with the silicon wafer, and the contact resistance is reduced.

[0054] In some embodiments of the present application, the first heating treatment can include increasing the temperature from a first temperature to a second temperature at a first temperature increasing rate; before the first heating treatment, the sintering treatment can further include a second heating treatment on the silicon wafer, the second heating treatment including increasing the temperature to the first temperature at a second temperature increasing rate and holding, the first temperature increasing rate being greater than the second temperature increasing rate. Thus, during the second heating treatment, the temperature can be increased to the first temperature at a smaller temperature increasing rate and held, thereby facilitating the removal of organic matter (debinding) in the paste, and then rapidly increasing the temperature at a larger temperature increasing rate in the first heating zone, so that the paste on the surface of the silicon wafer is melted and fully contacts the silicon wafer under the vibration field provided by the vibration generator, thereby reducing the contact resistance between the front grid lines and / or the aluminum back field lines and the silicon wafer, and the sintered front grid lines and / or aluminum back field lines are well shaped, which is conducive to improving the photoelectric conversion efficiency of the cell wafer.

[0055] In some embodiments of the present application, the second temperature increasing rate can be 10-15℃ / s, for example, the second temperature increasing rate can be 10℃ / s, 11℃ / s, 12℃ / s, 13℃ / s, 14℃ / s, 15℃ / s, etc. During the second heating treatment, the temperature is increased at a smaller temperature increasing rate, which is conducive to the removal of organic matter in the paste, thereby improving the conductivity of the front grid lines and / or the back field lines.

[0056] In some embodiments of the present application, the first temperature can be 390-410℃, for example, the first temperature can be 390℃, 395℃, 400℃, 405℃, 410℃, etc. Holding at the above temperature is conducive to the removal of organic matter in the paste.

[0057] In some embodiments of the present application, the holding time at the first temperature can be 18s-22s, for example, the holding time at the first temperature can be 18s, 19s, 20s, 21s, 22s, etc., the holding time within the above range is conducive to discharging the organic matter in the slurry, thereby facilitating the improvement of the conductivity of the front grid lines and / or the back field lines, and further improving the overall performance of the battery piece.

[0058] In some embodiments of the present application, the first temperature increasing rate can be 15℃ / s-25℃ / s, for example, the first temperature increasing rate can be 15℃ / s, 17℃ / s, 18℃ / s, 20℃ / s, 22℃ / s, 23℃ / s, 25℃ / s, etc., the first temperature increasing rate within the above range is conducive to keeping the front grid lines and / or the back field lines in good morphology, and is conducive to shortening the sintering time and reducing the production cost.

[0059] In some embodiments of the present application, the second temperature can be 810℃-850℃, for example, the second temperature can be 810℃, 820℃, 822℃, 825℃, 827℃, 828℃, 830℃, 840℃, 850℃, etc., rapidly increasing to the second temperature can quickly complete the high-temperature heating process, which is conducive to the shaping of the front grid lines and / or the back field lines, and makes the front grid lines and / or the back field lines after sintering keep good morphology.

[0060] In some embodiments of the present application, the sintering process after the first heating treatment can also include a cooling process. In some specific embodiments of the present application, after the first heating treatment, the battery piece can be transported in the cooling zone by the third conveying mesh belt 400 to reduce the temperature of the battery piece, and after the temperature of the battery piece is reduced to meet the requirements, the battery piece can be removed from the sintering device.

[0061] Reference Figure 3 and Figure 4 The front surface of the silicon wafer 10 is a textured surface 11, and the textured surface 11 has a plurality of pyramid structures, and there are gaps between adjacent pyramid structures. Figure 3 In the prior art, a vibration generator is not introduced during the sintering process, the wetting performance of the slurry is poor, and there is a cavity 2 between the front grid lines 20 and the silicon wafer 10 after sintering. Reference Figure 4 In the present application, a vibration generator is introduced during the sintering process, so that the surface tension of the molten slurry is reduced, the wetting performance of the slurry is good, and there is no cavity between the front grid lines 20 and the silicon wafer 10 after sintering, which is conducive to reducing the contact resistance between the front grid lines 20 and the silicon wafer 10.

[0062] Reference Figure 5 and Figure 6 The back surface of the silicon wafer 10 forms a back passivation layer 40, and a groove 41 is formed by laser processing. Figure 5In the prior art, no vibration generator is introduced in the sintering process, the wettability of the slurry is poor, and there is a cavity 2 between the back field line 30 and the silicon wafer 10 after sintering. In the present application, the vibration generator is introduced in the sintering process, which promotes the full contact of the slurry and the silicon wafer, and the back field line 30 and the silicon wafer 10 are in close contact after sintering. Figure 6 , and there is no cavity between the back field line 30 and the silicon wafer 10 after sintering.

[0063] In some embodiments of the present application, when laser grooving the original passivation layer, the laser spot can be about 30 μm, forming a back passivation layer 40 as shown in Figure 7 , which has a plurality of rows of grooves, and the longer grooves 41 and the shorter grooves 41 in each row are arranged alternately. During etching, a large number of laser spots are irradiated on the original passivation layer, and the longer grooves 41 are etched. A relatively small number of laser spots are irradiated on the original passivation layer, and the shorter grooves 41 are etched.

[0064] By depositing a back passivation layer on the back of the silicon wafer, the passivation of the silicon wafer can be achieved, the recombination of minority carriers on the back can be reduced, and the open-circuit voltage of the battery wafer can be improved. The aluminum paste has no burn-through capability for the silicon nitride layer, which results in that the aluminum back field cannot form an ohmic contact with the silicon wafer. By locally perforating the back, the contact between the aluminum back field and the silicon wafer can be improved, and the fill factor can be improved, but it may cause a certain degree of open voltage loss. The size of the laser spot used in the back laser grooving can be about 30 μm, and the perforation rate (the ratio of the total perforation area to the total area of the silicon wafer) is about 0.6%. Under the existing conditions, reducing the laser spot spacing or reducing the perforation rate may cause "cavities" at the contact position between the aluminum back field and the silicon wafer, resulting in an increase in series resistance and a decrease in fill factor. By introducing a low-frequency vibration field in the first sintering process, the contact between the aluminum back field and the silicon wafer can be improved, and the "cavities" can be reduced. Further, under the condition of keeping the perforation rate unchanged or reducing the perforation rate, the size of the laser spot can be reduced to improve the uniformity of the grooving area on the back of the silicon wafer, and better back passivation effect and ohmic contact between the aluminum back field and the silicon wafer can be obtained.

[0065] In some other embodiments of the present application, when laser grooving the original passivation layer, the laser spot can be adjusted to about 15 μm, and double laser lines are used for etching, forming a back passivation layer 40 as shown in Figure 8 or Figure 9 .

[0066] In some embodiments of the present application, referring to Figure 8 , Figure 9 and Figure 11The back passivation layer 40 has a plurality of groups of groove lines 3 arranged at intervals, each group of groove lines 3 corresponds to a back field line 30, and each group of groove lines 3 includes two or three groove columns 3', the extension direction of the groove column 3' is the same as that of the groove line 3, and each groove column 3' can include a plurality of grooves 41 arranged at intervals. Figure 8 and Figure 9 It can be seen that, after improving the slotting pattern of the back passivation layer, the distribution of the groove 41 sites on the back surface is more uniform, and the open-circuit voltage and the fill factor of the battery piece can be improved on the basis of maintaining or reducing the aperture ratio. In the present application, the diameter and arrangement of the laser spot can be adjusted by the parameters of the laser.

[0067] In another aspect of the present application, a solar cell is provided. In some embodiments of the present application, the solar cell can be prepared by the method described above. Thus, the front grid lines and / or the back field lines of the solar cell have good contact with the silicon wafer substrate, the contact resistance is small, and the solar cell has high reliability and photoelectric conversion efficiency.

[0068] In some specific embodiments of the present application, the solar cell can be a PERC cell.

[0069] In some embodiments of the present application, with reference to Figure 10 and Figure 11 The front surface of the silicon wafer 10 is a textured surface 11 having a plurality of pyramid structures with gaps between adjacent pyramid structures, and the front grid lines 20 have good contact with the silicon wafer 10; the back passivation layer 40 is located on the back surface of the silicon wafer 10, and can include a first passivation layer 42 and a second passivation layer 43, the second passivation layer 43 being located on the side of the first passivation layer 42 away from the silicon wafer 10. The back passivation layer 40 has grooves 41, and the back field lines 30 fill the grooves 41, and the back field lines 30 have good contact with the silicon wafer 10.

[0070] In some specific embodiments of the present application, the material of the first passivation layer 42 can include aluminum oxide, and the material of the second passivation layer 43 can include silicon nitride. The above-mentioned materials can have good back passivation effect, reduce recombination of minority carriers, and thus be conducive to improving the performance of the solar cell.

[0071] In some embodiments of the present application, with reference to Figure 10 One back field line 30 can correspond to one column of grooves 41. In some other embodiments of the present application, with reference to Figure 11 One back field line 30 can correspond to two columns of grooves 41.

[0072] The present application will be described in detail below by means of specific examples, and it will be understood by those skilled in the art that the specific examples below are merely for illustrative purposes and do not limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following examples, the conditions and methods known in the art can be used for processing.

[0073] Comparative Example 1

[0074] The silicon wafer was subjected to texturing, phosphorus diffusion, PSG removal, alkali etching, and annealing. A back passivation layer was deposited, which included an aluminum oxide layer and a silicon nitride layer, with the silicon nitride layer on the side of the aluminum oxide layer away from the silicon wafer.

[0075] The back passivation layer was subjected to slotting treatment using a laser, and the laser used for slotting had a spot size of 30 microns. After slotting, the structure of the back passivation layer can be referred to Figure 7 (Note that Figure 7 only shows the general appearance of the slotting of the back passivation layer and is not intended to limit the specific number of grooves).

[0076] In Comparative Example 1, the conveying mesh belt 1 shown in Figure 2 was used to transport the battery wafer in the sintering device, and conventional crystalline silicon cell sintering technology was used, gradually increasing the temperature from 200°C to a sintering peak temperature of 830°C at a rate of 10°C / s-15°C / s. After cooling, a solar cell was obtained.

[0077] The structure of the silicon wafer after sintering is shown in Figure 3 and Figure 5 . Due to the effect of surface tension, the paste cannot completely contact the silicon wafer after sintering, and there is a "void" at the interface. The presence of the "void" can lead to poor contact between the front grid lines 20, the back field lines 30, and the silicon wafer 10, reducing adhesion and increasing contact resistance, resulting in reduced reliability and photoelectric conversion efficiency of the crystalline silicon cell.

[0078] Example 1

[0079] The silicon wafer was subjected to texturing, phosphorus diffusion, PSG removal, alkali etching, and annealing. A back passivation layer was deposited, which included an aluminum oxide layer and a silicon nitride layer, with the silicon nitride layer on the side of the aluminum oxide layer away from the silicon wafer.

[0080] The back passivation layer was subjected to slotting treatment using a laser, and the laser used for slotting had a spot size of 30 microns. After slotting, the structure of the back passivation layer can be referred to Figure 7 (Note that Figure 7 only shows the general appearance of the slotting of the back passivation layer and is not intended to limit the specific number of grooves).

[0081] To avoid the appearance of "voids" in the sintering process, the sintering device shown in Figure 1 is used for sintering. The silicon wafer is placed in the second heating zone B, and first heated from 200°C to 400°C at a rate of 10°C / s-15°C / s, and then held for 20s to remove the glue. Then, the silicon wafer is placed in the first heating zone A, and rapidly heated from 400°C to a peak temperature of 830°C at a rate of 15°C / s-25°C / s. The heating rate in the first heating zone is greater than that in the second heating zone. A low-frequency vibration field with a frequency of 10Hz-1000Hz is introduced in the sintering process in this region. The vibration field is used to reduce the surface tension of the slurry and improve the wettability of the slurry. After cooling, a solar cell is obtained.

[0082] First, the temperature is increased to 400°C at a relatively small rate to ensure that the organic matter in the slurry is completely removed. Then, the temperature is rapidly increased while applying a low-frequency vibration field. Rapid sintering is beneficial to maintaining a good morphology of the front grid lines and / or back field lines. The low-frequency vibration field can effectively improve the contact effect of the slurry with the silicon wafer, and reduce the contact resistance of the front grid lines and / or back field lines. In combination with the joint action of rapid sintering and low-frequency vibration field, the front grid lines and back field lines after sintering are well shaped, and there is no "void" between the front grid lines 20 and the back field lines 30 and the silicon wafer 10, and the solar cell exhibits a high photoelectric conversion efficiency. Figure 4 Figure 6

[0083] Example 2

[0084] On the basis of Example 1, the back laser slotting pattern is optimized. The structure of the back passivation layer after slotting treatment can be referred to Figure 8 Figure 9 The sintering process is consistent with that of Example 1, and a vibration generator is used to assist the sintering process.

[0085] Example 2 optimizes the back laser slotting pattern on the basis of low-frequency sintering. A new back laser slotting pattern is designed. The laser spot diameter used in this pattern is about 15μm (only half of the conventional size). At the same time, the slotting line under a single back field is changed from one to two, and the slotting mode of a single line is more uniform. Compared with the conventional slotting pattern, the slotting pattern in Example 2 has a lower opening rate and the laser slotting sites are more uniformly distributed on the back. This can achieve a double improvement in open-circuit voltage and fill factor, and further improve the photoelectric conversion efficiency of the solar cell.

[0086] ​​​In the description of the specification, the description of the terms "one embodiment", "some embodiments", "some specific embodiments", and the like, means that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction. In addition, it should be noted that in the specification, the terms "first", "second", "third" are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0087] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A sintering apparatus characterized by comprising: The first heating zone comprises a first conveying mesh belt, the first conveying mesh belt has an upper part and a lower part, an upper surface of the upper part is used for placing the battery piece, and a lower surface of the upper part is in contact with a vibration generator.

2. The sintering apparatus according to claim 1, characterized by The vibration frequency of the vibration generator is 10 Hz-1000 Hz.

3. The sintering apparatus according to claim 1 or 2, characterized by The sintering device further comprises a second heating zone and a cooling zone, the second heating zone, the first heating zone and the cooling zone are arranged in sequence.

4. The sintering apparatus according to claim 3, wherein The second heating zone comprises a second conveying mesh belt, and the second conveying mesh belt is used for conveying the battery piece. And / or, the cooling zone comprises a third conveying mesh belt, and the third conveying mesh belt is used for conveying the battery piece.

5. A method of producing a solar cell, characterized by, The method comprises: providing a silicon wafer; forming an original passivation layer on a back surface of the silicon wafer; processing the original passivation layer by using a laser, removing part of the original passivation layer, and forming a back passivation layer with a plurality of grooves; printing paste on a front surface and the back surface of the silicon wafer; performing a sintering treatment on the silicon wafer with the printed paste, the sintering treatment comprising a first heating treatment, during the first heating treatment, the silicon wafer is placed above an upper part of a first conveying mesh belt, a lower surface of the upper part of the first conveying mesh belt is in contact with a vibration generator, and a vibration frequency of the vibration generator is 10 Hz-1000 Hz.

6. The method of claim 5, wherein, The first heating treatment comprises increasing a temperature from a first temperature to a second temperature at a first temperature increasing rate. Before the first heating treatment, the sintering treatment further comprises a second heating treatment on the silicon wafer, the second heating treatment comprises increasing the temperature to the first temperature at a second temperature increasing rate and holding the temperature, and the first temperature increasing rate is greater than the second temperature increasing rate.

7. The method of claim 6, wherein, At least one of the following conditions is met: The first temperature increasing rate is 15℃ / s-25℃ / s; The first temperature is 390℃-410℃; The second temperature is 810℃-850℃; The second temperature increasing rate is 10℃ / s-15℃ / s; The holding time at the first temperature is 18s-22s.

8. The method of claim 5, wherein, The back passivation layer has a plurality of groups of groove lines arranged at intervals, each group of groove lines corresponds to a back field line, and each group of groove lines comprises two or three groove columns.

9. The method according to any one of claims 5-8, characterized in that, After the first heating treatment, the sintering treatment further comprises a cooling treatment.

10. A solar cell, characterized by The solar cell is prepared by the method of any one of claims 5-9.

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