Solar cell and preparation method thereof

Abstract

The invention discloses a solar cell and a preparation method thereof. The preparation method of the solar cell comprises the following steps: providing a semi-finished solar cell with conductive paste formed in a preset area of a solar cell substrate; and electrifying the conductive slurry so as to carry out electrified sintering on the conductive slurry, so that the conductive slurry forms a conductive grid line on the solar cell substrate. Through the above mode, the preparation method of the solar cell provided by the invention can enable the heat of the conductive slurry to be transmitted from inside to outside, is higher in overall sintering efficiency, is less in heat overflow, can effectively avoid the damage to other functional layers, which are not resistant to high temperature, on the solar cell substrate, and improves the reliability of the solar cell. The contact time of the outer layer of the conductive slurry and air is extremely short, oxidation of the conductive grid line can be greatly reduced, the method is good in overall regulation and control performance and easy to regulate and control, the sintering quality can be accurately controlled, and over-burning or under-burning is avoided.

Description

Technical Field

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

[0002] Conductive pastes are widely used in fields such as photovoltaic cells. In the prior art, the sintering of conductive pastes for making metal electrodes of solar cells is generally carried out by tunnel furnace heating, for example, by direct radiation absorption of heating lamps and indirect heat transfer by hot circulating air to achieve the heating of the cell to the paste sintering temperature. Among them, the sintering in the sintering furnace seeks to form a better ohmic contact effect at the metal and semiconductor contact interface, which often causes the conductive particles in the conductive paste components to be sintered and over-melted, resulting in the line resistance of the grid line significantly deviating from the optimal state. There are other solutions, such as laser sintering, etc., whose mechanism is to radiate energy to the surface of the conductive paste, and after the conductive paste surface absorbs the heat, it transfers the heat to the deep part of the conductive paste. This method will form a temperature field gradient on the conductive paste with the temperature decreasing from the outside to the inside, which will cause the sintering of the conductive paste to have a uniformity difference.

[0003] In addition, due to the sensitivity of solar cell base materials or conductive pastes to temperature and the fact that substrate materials cannot withstand high temperatures for a long time, there is an urgent need to develop a conductive paste sintering method with little thermal impact on the base or short heating time. Summary of the Invention

[0004] The present application mainly provides a solar cell and a preparation method thereof to solve the above-mentioned problems existing in the existing sintering process.

[0005] To solve the above technical problems, the present application adopts a technical solution: providing a method for preparing a solar cell. The method for preparing a solar cell comprises:

[0006] Providing a semi-finished solar cell having a conductive paste formed in a predetermined area of ​​a solar cell substrate;

[0007] The conductive paste is electrified to electrically sinter the conductive paste, so that the conductive paste forms conductive grid lines on solar cells.

[0008] As a further example, before electrifying the conductive paste, the method further includes:

[0009] The semi-finished solar cell is dried.

[0010] As a further example, the process parameters of the electric sintering include: a current density of 0.1 mA / um 2 Above, the cumulative power-on time is greater than 0.1s.

[0011] As a further example, the process parameters of the electric sintering include: using direct current, the current intensity of the direct current is less than 100A, and the cumulative power-on time is greater than 0.1s; or, using pulse current, the pulse current amplitude is less than 10000A, the cumulative power-on time is greater than 0.1s, the pulse frequency is 10Hz~1000000Hz, and the duty cycle is 0.1~1.

[0012] As a further example, the step of electrifying the conductive paste includes:

[0013] First, the conductive paste is electrified in a constant voltage mode;

[0014] In response to the current flowing through the conductive paste reaching a preset current value, the constant voltage mode is switched to a constant current mode to maintain the preset current value continuously flowing through the conductive paste.

[0015] As a further example, the applying electricity to the conductive paste includes:

[0016] After electrification is applied to both ends of any continuous line of the conductive paste, the continuous line with electrification at both ends has a potential difference, and is electrically sintered under the action of the potential difference.

[0017] As a further example, the applying electricity to the conductive paste includes:

[0018] The conductive paste is electrified in multiple steps, and the process parameters of each step of the electrification sintering are the same or different.

[0019] As a further example, the electrifying the conductive paste includes: the number of electrified contact points of any continuous line in the conductive paste is 3 or more.

[0020] As a further example, after the step of electrically sintering the conductive paste, the method further includes:

[0021] Laser induced sintering is performed on the conductive grid lines to improve the electrical contact performance between the conductive grid lines and the solar cell substrate.

[0022] As a further example, the conductive paste is silver paste or silver-coated copper paste, and after sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -7 Ω·m.

[0023] As a further example, the conductive paste is copper paste, aluminum paste or nickel paste, and after sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -6 Ω·m.

[0024] As a further example, the contact resistivity between the conductive grid line and the solar cell substrate is no more than 10 mΩ·cm 2 .

[0025] As a further example, the solar cell substrate includes a conductive layer or a doped layer, and the predetermined area is located on the conductive layer or the doped layer.

[0026] As a further example, the conductive layer is a transparent oxide layer or a metal electrode layer.

[0027] To solve the above technical problems, the present application also adopts a technical solution to provide a method for preparing a solar cell, comprising:

[0028] Providing a semi-finished solar cell having a conductive paste formed in a preset area of ​​a metal seed layer;

[0029] The metal seed layer is electrified so that the conductive paste forms a conductive grid line.

[0030] As a further example, the process parameters of the electric sintering include: a current density of 0.1 mA / um 2 Above, the cumulative power-on time is greater than 0.1s.

[0031] According to another aspect of this patent, a solar cell is also proposed, which is prepared using any of the above-mentioned methods for preparing a solar cell.

[0032] The beneficial effects of the present application are: different from the prior art, the present application discloses a solar cell and a preparation method thereof, in which the conductive paste is subjected to electrical sintering so that the conductive paste is self-heated and heated as a whole, and a temperature gradient field with decreasing temperature from the outside to the inside, such as that generated by laser sintering, is not formed inside the conductive paste; and only the conductive paste that is energized generates heat, and relatively little heat overflows, thereby avoiding damage to other functional layers on the solar cell substrate that are not resistant to high temperatures; and, due to this electrical sintering method, heat is transferred from the inside of the conductive paste to the outside, and the time for the outer layer of the conductive paste to contact the air is extremely short, which can greatly reduce the oxidation of the conductive grid line.

[0033] Furthermore, by adjusting the current or voltage and the power-on time in the electric sintering process, the sintering process can be precisely controlled to avoid over-burning or under-burning, which is beneficial to improving the microstructure and performance of the conductive paste and the contact interface.

[0034] In addition, the solar cell preparation method provided in the present application has high sintering efficiency, fast sintering speed, and is more compatible with base metal slurry. It is extremely suitable for the sintering of base metal slurry and can avoid oxidation of base metal slurry during the sintering process (such as copper slurry oxidation); it is also suitable for main grid electrode design, providing a good industrialization method for further reducing the cost of manufacturing conductive grid lines using metal slurry.

[0035] Furthermore, the uneven conductive paste can be reinforced at weak locations, so that the conductive paste at the weak locations can be replenished to a certain extent, thereby achieving reinforced sintering of the high-resistance areas with weak conductive paste / gate lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0037] Figure 1 This is a schematic flow chart of an embodiment of a method for preparing a solar cell provided in the present application;

[0038] Figure 2 yes Figure 1 A top view of a semi-finished solar cell structure in the manufacturing method shown;

[0039] Figure 3 is Figure 1 A schematic structural diagram of a solar cell embodiment 1 obtained by the preparation method shown;

[0040] Figure 4 is Figure 1 A schematic structural diagram of a second embodiment of a solar cell obtained by the preparation method shown;

[0041] Figure 5 is Figure 1 A schematic structural diagram of a solar cell embodiment 3 obtained by the preparation method shown;

[0042] Figure 6 This is a comparison of SEM images of the conductive paste in heterojunction solar cells before and after sintering.

[0043] Figure 7 This is a comparison of the PL images of the conductive paste in the heterojunction solar cell before and after sintering.

[0044] Figure 8 This is a comparison of the SEM images of the conductive paste in the TOPCon battery before and after sintering.

[0045] Figure 9 This is a comparison of SEM images of the conductive paste in BC solar cells before and after electrical sintering.

[0046] Description of reference numerals:

[0047] 100-solar cell substrate;

[0048] 101-silicon substrate; 102-intrinsic amorphous silicon layer; 103-doped amorphous silicon layer; 104-transparent conductive oxide layer;

[0049] 111 - silicon substrate; 112 - boron-doped layer; 113 - tunneling oxide layer; 114 - phosphorus-doped polysilicon layer; 115 - passivation layer; 116 - metal electrode;

[0050] 121-silicon substrate; 122-front surface field; 123-passivation anti-reflection layer; 124-N region; 125-P region; 126-passivation layer;

[0051] 150-preset area; 152-conductive grid line;

[0052] 200-Solar cells. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0055] This application provides a method for preparing a solar cell. Figure 1 , Figure 1 : is a schematic flow chart of a method for preparing a solar cell provided in this application, the method for preparing a solar cell comprising:

[0056] Step 10: providing a semi-finished solar cell having a conductive paste formed on a predetermined area of ​​a solar cell substrate.

[0057] As an example of one of the conductive paste patterns, see Figure 2 , a top view of a semi-finished solar cell structure, the semi-finished solar cell includes a solar cell substrate 100, and a conductive paste located in a preset area 150 of the solar cell substrate 100, wherein the solar cell substrate 100 is a cell structure precursor before the conductive grid line of the solar cell is prepared, and the cell structure precursor can be a cell structure precursor of an existing conventional solar cell, and a conventional solar cell can be, for example, a heterojunction solar cell, a TOPCon cell (Tunnel Oxide Passivated Contact) or a BC cell (Back Contact Cell), etc.

[0058] In addition, the conventional solar cell can also be a combination of BC cell technology and other types of cell technology, such as IBC cell (Interdigitated Back Contact, cross back contact cell), TBC cell (TOPCon-IBC cell), HBC cell (Heterojunction Back Contact, heterojunction back contact cell), PBC cell (Passivated Back Contact, back contact P-type cell), HPBC cell (Hybrid Passivated Back Contact, composite passivated back contact cell) or HTBC (Heterojunction and Tunnel oxide passivated contact Back Contact, composite back contact cell using tunnel oxide passivation and heterojunction technology), etc.

[0059] The predetermined area may be a predetermined electrode preparation area or a prepared electrode area (eg, a metal seed layer).

[0060] It should also be noted that Figure 2 Only one pattern of the preset area 150 is shown. The figure indicates that the conductive paste pattern can be a pattern including multiple parallel paste units, each paste unit being a continuous line. In this example, it can be considered that the conductive grid lines ultimately formed by the conductive paste pattern are only auxiliary grid lines or main grid lines. The preparation method of the present application is not limited to this type of conductive paste pattern. For example, it can also be a grid or comb shape that is staggered horizontally and vertically. In this case, it can be considered that the pattern of the conductive paste is for forming main grid lines and auxiliary grid lines at the same time. Of course, it can also be other forms of patterns, which are specifically set according to the structure of the semi-finished solar cell and the grid line pattern that is actually desired to be formed.

[0061] It should be noted that the current sintering in this application can be performed by sintering the entire conductive paste pattern or by sintering only a portion of the pattern. When current flows only through a portion of the pattern, as one example, the portion of the conductive paste not flowing through the current can be sintered by heat transfer from the functional layer in contact with the conductive paste, but this method is certainly not limited to this.

[0062] The conductive paste contains a certain proportion of organic solvents, which help maintain the paste's fluidity and uniformity during its application to the pre-determined region 150 of the semi-finished solar cell. The conductive paste can be applied to the pre-determined region 150 of the semi-finished solar cell using methods such as screen printing or laser transfer. At this point, the conductive paste is in a wet state and can be formed into any conductive pattern based on design requirements.

[0063] More specifically, the conductive paste is formed in a predetermined region 150 of a functional layer on the surface of the solar cell substrate 100. This functional layer can be a conductive layer, such as a transparent oxide layer in a heterojunction solar cell, or a pre-prepared metal electrode layer on the back of a TOPCon cell. This functional layer can also be an N-region doped layer or P-region doped layer in a BC cell, or a doped region on the front or back of a TOPCon cell. The doped region can also be referred to as a doped layer. The functional layer is determined based on the specific solar cell type and is not specifically limited in this application.

[0064] It should also be noted that when the functional layer is a metal electrode layer (or seed layer), that is, when the conductive paste is prepared on the metal electrode layer, the line resistivity of the conductive paste below does not include the metal electrode layer.

[0065] The above examples illustrate that any type of solar cell that requires the use of conductive paste to form conductive grid lines is suitable for production using the technology provided in this application. This application will no longer list other types of solar cells and specific functional layers one by one.

[0066] Furthermore, the conductive paste can be either low-temperature or high-temperature, with compatibility with the solar cell materials used and performance at specific temperatures being considered when selecting the right paste. Low-temperature pastes are suitable for heat-sensitive materials, while high-temperature pastes are suitable for applications that must withstand higher temperatures. The performance of the conductive paste directly impacts the efficiency of the solar cell, necessitating precise control of the paste's composition and printing process.

[0067] The components of conductive paste usually include metal particles, glass powder and organic carriers. Metal particles are commonly silver, copper, aluminum, etc. Metal particles are used to provide conductivity and are the core functional materials of conductive paste; glass powder acts as a binder to promote ohmic contact between metal particles and silicon wafers, and form a good contact interface during the sintering process; organic carriers are used to adjust the rheological properties, viscosity and coating (such as screen printing or laser transfer) performance of the conductive paste, which mainly contains solvents, resins and other additives.

[0068] Based on design requirements, the specific composition, particle size, proportion of each component, etc. of the conductive paste can be adjusted to form high-temperature conductive paste and low-temperature conductive paste commonly used in the photovoltaic field. Both high-temperature conductive paste and low-temperature conductive paste are suitable for the technical solution of this application.

[0069] Step 20: electrify the conductive paste to electrically sinter the conductive paste, so that the conductive paste forms conductive grid lines on the solar cell.

[0070] It should be noted that the power sintering in this application can refer to forming a fixed connection between the conductive paste and the solar cell substrate (i.e., the functional layer in contact with the conductive paste) (which can also be called curing in this case), and also guides the paste to form a good ohmic contact with the solar cell substrate. Considering that when the power sintering is performed, the current preferentially flows along the conductive paste, causing the conductive paste to self-heat, the power sintering in this application mainly improves the line resistivity of the conductive grid line, and at the same time, it can also improve the contact resistivity between the conductive paste and the solar cell substrate.

[0071] Specifically, after the conductive paste is electrified, when the current flows through the conductive paste, when the current flows through the conductive paste with a large resistance, according to Joule's law, Q=I 2 Rt, Q is the heat generated (unit: joule, J); I is the current passing through the conductor (unit: ampere, A); R is the resistance of the conductor (unit: ohm, Ω); t is the time the current passes (unit: second, s). The conductive paste itself will generate heat due to resistance. The heat generated causes the organic carrier in the conductive paste to evaporate, and promotes the smelting and sintering of metal particles and glass powder to form a stable and continuous conductive path. The heat generated in the process makes the metal particles in the conductive paste fully melt and closely contact the functional layer on the surface of the solar cell substrate 100, and the contact interface also reaches the sintering temperature, so that the conductive paste forms a good ohmic contact with the functional layer below. The heating process can also effectively eliminate the tiny pores in the conductive paste layer and reduce the resistivity of the material. Finally, after a certain power-on time, the conductive paste is sintered as a whole to obtain a conductive grid line.

[0072] After the conductive paste is sintered through electrical current, the conductive grid lines themselves are solidified, and their resistivity is significantly reduced compared to before sintering, that is, their conductivity is improved, and their contact resistance with the functional layer is improved and reduced.

[0073] Specifically, by directly applying voltage and / or current to the conductive paste through an external power supply, the conductive paste will generate a large amount of heat under the action of the external power supply. The area with greater resistance of the conductive paste will generate higher heat. When the accumulated heat reaches the temperature required for the conductive paste components to solidify or sinter, the conductive paste forms a conductive grid line.

[0074] Electric sintering directly uses electric current to heat the conductive paste itself, reducing energy loss. Compared with the traditional furnace heating sintering method, electric self-heating can quickly increase the temperature of the conductive paste and the contact interface with the solar cell substrate in a short period of time, achieving rapid heating; and electric sintering can control the line resistivity of the conductive grid line within the optimal range. By adjusting the current or voltage and the power-on time in the electric sintering process, the sintering process and the final sintering temperature can be precisely controlled, which is beneficial to improving the microstructure and performance of the interface contact between the conductive paste and the solar cell substrate. Electric sintering of the conductive paste can achieve a fast and uniform sintering effect. This electric sintering technology not only improves production efficiency, but also reduces thermal damage and maintains the high efficiency performance of solar cells.

[0075] Especially in the field of solar cells, when the conductive paste applied in step 10 is uneven, or when some areas of the conductive paste have a small cross-sectional area, the resistance of the local area is large, and the Joule heat generated during sintering is large, that is, the sintering temperature generated is high, which can make the paste in the adjacent area have a certain fluidity, that is, the paste components in the adjacent area can flow to the uneven or narrow area after melting to repair the conductive material. Therefore, the weak area is repaired by the conductive paste in the adjacent area, so that the process provided by the present application also has the effect of strengthening the weak area of ​​the conductive paste, and realizes the reinforcing sintering of the high-resistance area with weak shape.

[0076] As another example, when power is applied to both ends of any continuous line of the conductive paste, the continuous line has a potential difference, and is electrically sintered under the action of the potential difference; once all continuous lines are powered, the entire conductive paste is electrically sintered. Those skilled in the art will understand that, to achieve the overall sintering effect of the conductive paste, all continuous lines in the conductive paste pattern must be powered at least once. However, if some continuous lines in the conductive paste pattern are not electrically sintered, this does not constitute a limitation of this application and is also protected by this application.

[0077] More specifically, the method of applying power to all the continuous lines of the conductive paste pattern is not limited, as long as current flows through all the positions of the conductive paste pattern.

[0078] As another embodiment, the number of energized contact points for any continuous line in the conductive paste is three or more. Specifically, for example, the energized device has three, four, or five or more contact electrodes, each contact electrode forming an energized contact point with the conductive paste. Each contact electrode is connected to a continuous line in the conductive paste at intervals, and each contact electrode distributed along the continuous line forms a potential difference, thereby simultaneously sintering the entire conductive paste in sections. Specifically, it is sufficient that the potentials of the energized contact points are different after power is applied. As one example, as the number of energized contact points increases, the voltage or potential in the closed loop of the circuit system shows a decreasing trend.

[0079] In another embodiment, between step 10 and step 20, the conductive paste is dried in advance, and then the dried conductive paste is electrically sintered. This helps to reduce the duration and energy consumption of the electrical sintering and improve the efficiency of the electrical sintering.

[0080] Specifically, before step 20, the preparation method further includes: drying the semi-finished solar cell with the conductive paste formed in the preset area to obtain dry conductive paste.

[0081] In step 10, the preset area 150 of the solar cell substrate 100 is coated with a wet conductive paste, and then the semi-finished solar cell with the conductive paste formed in the preset area is placed in a drying device for drying. The drying device can be a heating device such as an oven or a heating table, or it can be an air drying chamber, etc. The air drying chamber can naturally dry the conductive paste. This application does not limit the specific type of the drying device, as long as it can convert the wet conductive paste into a dry conductive paste.

[0082] Among them, when the drying device is a heating device, the temperature during drying is lower than the sintering temperature reached during the power-on sintering process, and is also lower than the sintering temperature of a traditional tunnel furnace. It only needs to be able to dry the wet conductive paste.

[0083] After drying, the conductive paste changes from a fluid state to a semi-solid state, most of the organic carriers it contains are evaporated and removed, and its conductivity is improved, which is helpful for subsequent electrical sintering.

[0084] After drying, the conductive paste is in a semi-solid state, that is, a small amount of organic carrier is still retained in the conductive paste to ensure that the conductive paste has a certain fluidity in the early stage of sintering and promote the contact and densification between the metal particles.

[0085] Drying can remove most of the organic carrier, which can prevent defects such as grid line cracking and grid breakage caused by rapid evaporation of solvent during electric sintering. At the same time, the drying step helps to reduce the thermal stress of the conductive paste during the subsequent electric sintering process, further improving the stability and yield of electric sintering.

[0086] Furthermore, the process parameters for the electric sintering of the conductive paste in step 20 include: a current density of 0.1 mA / um 2 The cumulative power-on time is greater than 0.1s. Furthermore, the current density is, for example, 0.2mA / um 2 、0.4mA / um 2 、0.8mA / um 2 、1mA / um 2 、2mA / um 2 、5mA / um 2 、10mA / um 2 、20mA / um 2 、50mA / um 2 、80mA / um 2 、100mA / um 2 、200mA / um 2 、300mA / um 2 、500mA / um 2 、800mA / um 2 、1000mA / um 2 etc., minimum current density 0.1mA / um 2 The sintering / curing effect can be achieved, and the line resistivity can be reduced. The other current densities mentioned above can achieve even better sintering / curing effects, making the line resistivity of the conductive grid lines close to its optimal line resistivity. It should be noted that this current density value example takes into account both DC power supply and pulse current power supply. When using a pulse current power supply, the current density of its single pulse current can be relatively high.

[0087] Furthermore, the cumulative power-on time is, for example, 0.5s, 1s, 2s, 5s, 8s, 10s, 15s, 20s, 30s, 50s, 60s, 80s, 100s, 120s, 150s, 180s, 200s, 300s, 400s, 500s, 600s, 800s, 1000s, 1200, 1500s, 1600s, 1800s, etc., wherein, at different current densities, the adaptation time is different. At low current density, a longer time is required to achieve better sintering / curing effect. At high current density, a shorter time is required to adapt. If the time is too long, it may cause problems such as gate line fusing. The above-mentioned cumulative power-on time takes into account the various scenarios of conductive paste sintering and the available current density, which can achieve the best line resistivity while not overburning.

[0088] Further preferably, the process parameters of the electric sintering of the conductive paste in step 20 include: a current density range of 0.1 mA / um 2~500mA / um 2 , the cumulative power-on time range is 0.1s to 600s. Within this preferred parameter range, the conductive paste is rapidly sintered / cured, the internal organic matter is rapidly volatilized, and the conductive grid line structure formed after the conductive paste is sintered / cured has high consistency. From the longitudinal cross-section of the grid line (parallel to the width direction of the conductive grid line), the cross-sectional shape of the grid line can be maintained at more than 85%, that is, the ability of the grid line cross-section of all line segments to maintain the shape of the grid line is more than 85%. In this way, the line resistivity uniformity of the grid line is achieved at more than 85%, and in some instances, it can even exceed 95%. That is to say, under this preferred condition, the conductive grid line formed after the conductive paste is sintered can have a line resistivity with optimal uniformity.

[0089] Electric sintering can be achieved by direct current or pulse current, as long as the current density flowing through the conductive paste reaches 0.1mA / um 2 The above is sufficient, and this application does not limit the specific current form.

[0090] As another embodiment, the process parameters of the electric sintering include: using a direct current power supply to sinter the conductive paste, wherein the direct current intensity is less than 100A, and the cumulative power-on time is greater than 0.1s, for example, the direct current intensity is 2A, 5A, 10A, 15A, 20A, 50A, 80A, 90A, 95A, etc.; or using a pulse current power supply to sinter the conductive paste, wherein the pulse current amplitude is less than 10000A, and the cumulative power-on time is greater than 0 .1s, the pulse frequency is 10Hz~1000000Hz, the duty cycle is 0.1~1, for example, the pulse current amplitude is 10A, 100A, 500A, 1000A, 5000A, 9500A, etc., for example, the pulse frequency is 10Hz, 50Hz, 100Hz, 1000Hz, 100000Hz, 1000000Hz, etc., for example, the duty cycle is 0.1, 0.2, 0.5, 0.8, 1, etc. These electric sintering methods can make the current density through the conductive paste reach 0.1mA / um 2 above, thereby achieving effective sintering.

[0091] When the current density through the conductive paste reaches 0.1mA / um 2When the temperature is above 5000 K, the metal particles in the conductive paste generate enough heat under the action of the electric current. Under the action of high temperature, the contact areas between the metal particles begin to combine to form inter-particle contact. At this time, the line resistance of the conductive paste begins to decrease, and the high temperature causes the organic carrier in the conductive paste to evaporate fully. The glass powder in the conductive paste acts as a solvent in the early stage of sintering, which can improve the sintering characteristics of the conductive paste, promote the bonding of the metal particles with the interface of the solar cell substrate, and finally form electrical contact. During the sintering process, an interface layer is formed between the solar cell substrate and the conductive paste, which not only helps to reduce the contact resistivity, but also enhances the mechanical strength of the interface. As the sintering temperature increases, the bonding between the metal particles gradually strengthens, and the line resistance continues to decrease. After a certain power-on time, a conductive grid line with significantly improved structural uniformity can be formed.

[0092] Optionally, the conductive paste can be directly sintered without drying. In this case, since the conductive paste is wet and contains a large amount of organic carriers, a higher current density and / or a longer sintering time can be used to ensure effective sintering.

[0093] For example, the wet conductive paste is directly sintered by electricity, and the current density used can be 0.5mA / um 2 , the power-on time is extended to 10s, which can also allow the wet conductive paste to be sintered into the conductive grid line 152.

[0094] It should be noted that, in view of the characteristics of the conductive paste, such as the metal particle size, the content and composition of organic and inorganic additives, and the characteristics of the glass material, the process parameters of the electric sintering need to be optimized accordingly to adapt to the appropriate current density and power-on time, so as to improve the sintering efficiency and the quality of the formed conductive grid lines.

[0095] As another embodiment, electrifying the conductive paste includes electrifying the conductive paste in multiple steps to improve the sintering efficiency and control the sintering quality, wherein the process parameters of each step of the electrified sintering are the same or different. Process parameters include current intensity and electrification time. Among them, it can be completed in two steps, three steps or more steps. By adjusting the current intensity and electrification time in stages, the sintering process can be accurately regulated to ensure that the metal particles in the gate line are fully combined, while effectively reducing the risk of over-burning or under-burning, and ultimately achieving a conductive gate line 152 with uniform and consistent line resistivity. On the other hand, it also improves the contact characteristics between the gate line and the silicon substrate or the surface functional layer, that is, reduces the contact resistivity, and comprehensively improves the overall electrical performance of the solar cell.

[0096] For example, in one example, stage 1: DC current 10A, power-on time 0.05s; stage 2: DC current 30A, power-on time 0.1s; stage 3: DC current 20A, power-on time 0.05s; stage 4: DC current 5A, power-on time 0.05s. The specific number of steps and the process parameters for each step are not limited to these, and are determined by the actual battery type, conductive paste properties, and power sintering requirements.

[0097] The cumulative power-on time mentioned above may refer to the time when direct current is used, the sum of the effective action time when pulse current is used, or the sum of the time of each step when multi-step power-on sintering is performed.

[0098] It should also be noted that when the process is performed in multiple steps, the same continuous line of the conductive paste can be energized in multiple steps, or different continuous lines in the conductive paste can be energized in multiple steps. As one example, the energizing device is sequentially connected to different locations of the conductive paste to sinter the conductive paste in sections. For example, the conductive paste is divided into two, three, or four continuous sections, and the energizing device sequentially energizes and sinters each section of the conductive paste.

[0099] More specifically, as an example of sintering the conductive paste in multiple steps, step 20 of energizing the conductive paste and maintaining the energization for a preset time period specifically includes:

[0100] Applying electricity to the conductive paste with a first electrical parameter and maintaining the electricity supply for a first time period;

[0101] Applying electricity to the conductive paste with a second electrical parameter and maintaining the electricity supply for a second time period;

[0102] applying electricity to the conductive paste with a third electrical parameter and maintaining the electricity applied for a third time period;

[0103] The conductive paste is electrified with a fourth electrical parameter and kept electrified for a fourth time period.

[0104] Among them, the value of the second electrical parameter is the largest, and the values ​​from the second electrical parameter to the fourth electrical parameter gradually decrease; the second time length is greater than the first time length, the third time length and the fourth time length.

[0105] The above-mentioned electrical parameters may be current or voltage. The value of the first electrical parameter is smaller than the value of the second electrical parameter, and the values ​​of the second electrical parameter to the fourth electrical parameter gradually decrease.

[0106] The conductive paste is energized with the first electrical parameter and maintained for the first time, which is mainly used to further dry the conductive paste, evaporate the remaining organic carrier, and make the metal particles in the conductive paste form preliminary contact; then, the conductive paste is energized with the second electrical parameter and maintained for the second time, so that after a better conductive path is formed in the conductive paste, the sintering temperature can be efficiently increased, the close bonding between the metal particles is promoted, a stable conductive network is formed, and the conductive paste and the solar cell substrate 100 are promoted to form a contact structure; then, the conductive paste is energized with the third electrical parameter and maintained for the third time, which further optimizes the conductive path, prevents overburning, and ensures conductive performance; finally, the conductive paste is energized with the fourth electrical parameter and maintained for the fourth time, which can prevent underburning, consolidate the sintering effect, and improve the overall quality of the conductive grid line 152.

[0107] More specifically, as another example of sintering the conductive paste in multiple steps, the conductive paste is energized and maintained energized for a preset time in step 20, specifically including:

[0108] Passing power to the conductive paste with a pulse current having a first amplitude and a first duty cycle for a first time period;

[0109] Passing power to the conductive paste for a second period of time using a pulse current having a second amplitude and a second duty cycle;

[0110] The conductive paste is energized with a pulse current having a third amplitude and a third duty cycle for a third time period.

[0111] The values ​​from the first amplitude to the third amplitude gradually decrease, and the values ​​from the first duty cycle to the third duty cycle also gradually decrease.

[0112] In other words, during the electric sintering process, in the early stage, a pulse current with a large current peak and a large duty cycle is selected to energize the conductive paste. The conductive paste plate is rapidly heated by the pulse current with a large peak and a large duty cycle, so that the organic carrier in the conductive paste evaporates rapidly and promotes the rapid formation of contact between the metal particles; in the middle stage, a pulse current with a moderate current peak and a duty cycle is used, and the large current formed in the conductive paste is used for electric sintering, so that the metal particles are quickly interconnected, which promotes the close bonding between the metal particles, and can form a stable conductive network, and promote the conductive paste to form a contact structure with the solar cell substrate 100; in the later stage, a pulse current with a small current peak and a duty cycle is used to continue to energize the conductive paste to keep the conductive paste warm, so as to promote the formation of a stable and reliable interconnection structure between the metal particles, effectively reduce the defects and unevenness in the sintering process, and can significantly reduce the line resistivity of the formed conductive grid line 152.

[0113] In another embodiment, the step 20 of applying electricity to the conductive paste specifically includes:

[0114] First, the conductive paste is energized using a constant voltage mode;

[0115] In response to the current flowing through the conductive paste reaching a preset current value, the constant voltage mode is switched to the constant current mode, and the preset current value is maintained to continue to flow through the conductive paste until the conductive paste is sintered to form the conductive grid lines on the solar cell.

[0116] In constant voltage mode, the power supply maintains the set voltage value, while the current gradually increases as the resistance of the conductive paste decreases. When the current reaches the preset current value, the constant voltage mode switches to constant current mode. The current flowing through the conductive paste is maintained at the preset current value, while the voltage decreases as the resistance of the conductive paste decreases until the conductive paste is sintered to form the conductive grid lines on the solar cell.

[0117] In this embodiment, in constant voltage mode, a relatively high voltage is used to rapidly evaporate the organic carrier in the conductive paste and promote contact between the metal particles. Subsequently, in constant current mode, a predetermined current value is maintained through the conductive paste, forming a stable conductive structure between the metal particles and promoting contact between the conductive paste and the solar cell substrate 100. This energized sintering process ensures uniform and thorough sintering of the conductive paste, avoiding local overheating or insufficient sintering, and optimizing the performance of forming the conductive grid lines 152 and their contact with the solar cell substrate 100.

[0118] In another embodiment, after the conductive paste is subjected to a single electrical sintering, a secondary laser induced sintering may be performed. After step 20, the preparation method further includes: performing laser induced sintering on the conductive grid lines to further improve the electrical contact performance between the conductive grid lines and the solar cell substrate.

[0119] Laser induced sintering can further reduce the contact resistance at the contact interface between the conductive grid line 152 and the solar cell substrate 100, further improve the electrical contact performance between the conductive grid line 152 and the solar cell substrate 100, and help reduce the recombination of charge carriers at the interface, thereby improving the overall photoelectric conversion efficiency of the solar cell.

[0120] By combining primary electric sintering with secondary laser-induced sintering, the electrical performance and mechanical adhesion strength of the conductive grid line 152 can be significantly improved. The electric sintering can improve the line resistivity of the conductive grid line 152 and its contact resistivity with the solar cell substrate 100. The secondary laser-induced sintering can further reduce the contact resistivity at the contact interface between the conductive grid line 152 and the solar cell substrate 100, thereby achieving better electrical connectivity and improving the photoelectric conversion efficiency of the solar cell.

[0121] The type of conductive paste in this application is not limited.

[0122] As one embodiment, the conductive paste is silver paste or silver-coated copper paste. After sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -7 Ω·m.

[0123] As one embodiment, the conductive paste is copper paste, aluminum paste or nickel paste. After sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -6 Ω·m.

[0124] Furthermore, the contact resistance between the conductive grid line and the solar cell substrate 100 does not exceed 10 mΩ·cm 2 , where the contact resistivity here mainly refers to the contact resistivity between the guiding grid line and the silicon substrate.

[0125] According to another aspect of the present application, a method for preparing a solar cell is also provided, comprising:

[0126] Providing a semi-finished solar cell having a conductive paste formed in a preset area of ​​a metal seed layer;

[0127] The metal seed layer is electrified, and the metal seed layer generates heat by self-heating and transfers it to the conductive paste. At the same time, the current is transferred from the metal seed layer to the conductive paste, causing the conductive paste to self-heat, thereby forming a conductive grid line.

[0128] Specifically, the metal material used for the metal seed layer is, for example, any one of nickel, copper, aluminum, silver, chromium, gold, and tin, or an alloy thereof. The metal seed layer can be prepared by screen printing, chemical deposition, or physical deposition. The solar cell preparation method provided in this embodiment can also achieve sintering of the conductive paste, providing a good industrial method for further reducing the cost of manufacturing conductive grid lines using metal paste.

[0129] Furthermore, the process parameters of the electric sintering include: the current density is 0.1mA / um 2 The cumulative power-on time is greater than 0.1 s. The current density and the cumulative power-on time can refer to the examples listed in the above embodiment.

[0130] According to another aspect of this patent, a solar cell 200 is also provided, which is prepared using the solar cell preparation method described in any of the above embodiments. The solar cell 200 can be a heterojunction solar cell, a TOPCon cell, or a BC cell, etc., which will not be described in detail.

[0131] Example 1

[0132] The solar cell is a heterojunction cell.

[0133] 1. Velveting and cleaning

[0134] like Figure 3 As shown, a tiny pyramid structure is formed on the surface of the silicon substrate 101 by chemical etching to increase light absorption efficiency. The silicon wafer is cleaned to ensure that the surface is clean and free of contamination.

[0135] 2. Depositing an intrinsic amorphous silicon layer 102

[0136] A layer of intrinsic amorphous silicon 102 is deposited on both sides of the silicon substrate 101 using plasma enhanced chemical vapor deposition (PECVD) technology, which serves as a passivation layer to reduce surface recombination loss.

[0137] 3. Deposition of doped amorphous silicon layer 103

[0138] A P-type doped amorphous silicon layer 103 and an N-type doped amorphous silicon layer 103 are deposited on the intrinsic amorphous silicon layer 102 to form a pin or nip structure, thereby constructing a heterojunction.

[0139] 4. Depositing a transparent conductive oxide layer 104

[0140] A transparent conductive oxide layer 104 (such as TCO, ITO or AZO) is deposited on the P-type doped amorphous silicon layer 103 and the N-type doped amorphous silicon layer 103 on both sides of the doped amorphous silicon layer. This step is particularly important for the front contact because it not only needs to have high conductivity but also good transmittance to incident light.

[0141] 5. Preparation of electrodes

[0142] Conductive paste is coated on the transparent conductive oxide layer 104 on both sides of the silicon substrate 101 by screen printing or other methods, and then the conductive paste is dried; the dried conductive paste is electrically connected and sintered to form the conductive gate line 152.

[0143] The conductive paste used in this embodiment is a silver-coated copper conductive paste. By applying a direct current of 1A-10A across the conductive paste for less than 1 second, the formed conductive gate lines 152 can form good contact with the transparent conductive oxide layer 104 without damaging the doped amorphous silicon layer 103. The sintering time is much shorter than that of furnace sintering, effectively avoiding the problem of copper-containing conductive paste being easily oxidized when used as conductive gate lines.

[0144] The test results show that after the conductive paste is sintered by electricity in this embodiment, the line resistivity of the conductive paste increases from 5.2×10 -6 Ω·m is reduced to 2.0×10 -8 Ω·m; minority carrier lifetime from 1600ms to 1590ms. Figure 7The brightness of the photoluminescence (PL) image remains almost unchanged. From the stable state of the minority carrier lifetime and the PL image, it can be seen that the electric sintering process used in this embodiment has almost no effect on the substrate of the heterojunction solar cell.

[0145] Further, see Figure 6 and Figure 7 ,in Figure 6 This is a comparison of SEM (Scanning Electron Microscope) images of the conductive paste in the heterojunction solar cell before and after sintering. Figure 7 This is a comparison of the PL (Photoluminescence) images of the conductive paste in the heterojunction solar cell before and after sintering.

[0146] Figure 6 (a) is a SEM image of the contact interface between the conductive paste and the transparent conductive oxide layer 104 before sintering, and (b) is a SEM image of the contact interface between the conductive grid line 152 and the transparent conductive oxide layer 104 formed after sintering. It can be clearly seen from the comparison that after sintering, the interconnection structure between the metal particles is dense, the structural uniformity is significantly improved, and the particles are tightly bonded, thereby enhancing the conductivity. Figure 6 In (a) and (b), it can be observed that the conductive paste exhibits better consistency after electrical sintering.

[0147] Figure 7 (a) is the PL image of the semi-finished solar cell substrate before sintering, and (b) is the PL image of the solar cell after sintering. Figure 7 Comparison of the PL images shows no significant decrease in the photoluminescence intensity of the solar cell after electrical sintering, indicating that the sintering process has no negative impact on the photovoltaic properties of the solar cell. These results demonstrate the applicability and effectiveness of the electrical sintering process in this example for heterojunction solar cells.

[0148] also, Figure 7 The PL image shows that despite the electric sintering process, the luminescence performance of the material is still maintained at a high level, which further confirms the superiority of the electric sintering method. It does not affect the passivation effect of the intrinsic amorphous silicon layer 103 and the doped amorphous silicon layer 104, nor does it increase the interface defects between the silicon substrate 101 and the intrinsic amorphous silicon layer 102.

[0149] In summary, the electric sintering technology not only shortens the production cycle of heterojunction solar cells and reduces energy consumption, but also significantly optimizes the contact interface between the conductive paste and the transparent conductive oxide layer 104, thereby significantly improving the performance of heterojunction solar cells.

[0150] Example 2

[0151] The solar cell is a TOPCon cell.

[0152] 1. Cleaning and velveting:

[0153] like Figure 4 As shown, specifically, the silicon substrate 111 is textured on both sides to form a pyramid texture structure.

[0154] 2. Diffuse boron on the front surface of the silicon substrate 111 to form a boron-doped layer 112;

[0155] 3. Remove the BSG layer plated on the back side and perform alkaline polishing on the back side of the silicon substrate 101;

[0156] 4. Prepare a tunneling oxide layer 113 on the back side of the silicon substrate 111 and deposit an intrinsic amorphous silicon layer;

[0157] The tunnel oxide layer 113 and the intrinsic amorphous silicon layer are grown on the back side of the silicon substrate 111 by using the LPCVD method. The thickness of the tunnel oxide layer 113 is 1 nm to 5 nm, and the thickness of the intrinsic amorphous silicon layer is 50 nm to 150 nm.

[0158] 5. Phosphorus is diffused on the back side of the silicon substrate 111 to form a phosphorus-doped polysilicon layer 114 and PSG (borosilicate glass);

[0159] In this step, the thickness of the phosphorus-doped polysilicon layer 114 is 50 nm to 150 nm, and the doping amount is 5E18 to 3E21 cm -3 .

[0160] 6. Remove the PSG coated on the front and side surfaces of the silicon substrate 111, clean and remove the polysilicon layer, and remove the front BSG and back PSG;

[0161] 7. Prepare a passivation layer 115 on the front and back sides of the silicon substrate 111;

[0162] In this step, the passivation layer 115 on the front side of the silicon substrate 111 can be a dielectric layer composed of one or more of an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer. For example, it can be a double-layer dielectric layer of aluminum oxide and silicon nitride. The passivation layer 115 on the back side of the silicon substrate 111 can be a silicon nitride layer.

[0163] 8. Coating the slurry on the back side of the silicon substrate 111 to prepare a thinner metal electrode 116, which is a silver electrode;

[0164] 9. Prepare a front electrode on the front side of the silicon substrate 111;

[0165] 10. Print a base metal conductive paste on the metal electrode 116. The base metal conductive paste is a silver-coated copper conductive paste. Dry the cell coated with the base metal conductive paste. Apply a pulse current to both ends of the conductive paste. Electrically connect the dried base metal conductive paste to cause it to self-heat. Apply electricity to sinter it to form a conductive grid line 152. The conductive grid line 152 and the metal electrode 116 constitute the back electrode. The pulse current amplitude used in the electrical sintering is less than 100A, the cumulative power-on time is greater than 0.1s, the pulse frequency is 100,000Hz, and the duty cycle is 0.5. After the electrical sintering, the line resistivity of the conductive paste increases from 4.51×10 -6 Ω·m is reduced to 3.27×10 -8 Ω·m;

[0166] 11. Light injection processing;

[0167] 12. After laser-induced sintering (LIS), the contact resistivity between the back electrode and the silicon substrate dropped to below 0.8 mΩ cm², improving the photoelectric conversion efficiency of the TOPCon cell. LIS improved the ohmic contact, and galvanic sintering enabled the application of base metal slurries.

[0168] It should be noted that Figure 4 Not all front and back electrodes are shown.

[0169] See Figure 8 , Figure 8 This is a comparison of the SEM images of the conductive paste in the TOPCon battery before and after sintering. Figure 8 (a) is a SEM image of the contact interface between the conductive paste (the base metal paste mentioned above) and the metal electrode 116 before sintering, and (b) is a SEM image of the contact interface between the conductive gate line 152 and the metal electrode 116 formed after sintering. Figure 8 (a), Figure 8 (b) clearly shows that the contact interface between the conductive grid line 152 and the metal electrode 116 is closer after electrical sintering, which is beneficial to improving the current transmission efficiency.

[0170] By comparing Figures (a) and (b), it can be seen that the electric sintering significantly improves the interface characteristics between the conductive paste and the metal electrode 116, reduces the contact resistance between the conductive grid line 152 and the metal electrode 116, and improves the overall performance of the TOPCon battery.

[0171] Example 3

[0172] The solar cell is a BC cell.

[0173] 1. If Figure 5As shown, a semi-finished BC solar cell with electrodes to be fabricated is provided. Specifically, the semi-finished BC solar cell includes a silicon substrate 121, a front surface field 122 and a passivation anti-reflection layer 123 located on the front surface of the silicon substrate 121, a P region 124 (P-type doped region) and an N region 125 (N-type doped region) located on the back surface of the silicon substrate 121, and a passivation layer 126. The passivation layer 126 may have grooves formed at locations corresponding to the N region 124 and the P region 125, so that the conductive paste contacts the N region 124 and the P region 125, respectively, through the corresponding grooves.

[0174] 2. Preparation of electrodes

[0175] Conductive paste is applied to the slots (also referred to as the predetermined areas 150) using screen printing or other methods, and then dried. The dried conductive paste is electrically connected and then sintered to form conductive gate lines 152. The current intensity is 1A-10A, and the sintering time is 10 seconds. After sintering, the conductive gate lines 152 formed by the conductive paste form ohmic contacts with the corresponding N-regions 124 and P-regions 125.

[0176] See Figure 9 , Comparison of SEM images of the conductive paste in BC solar cells before and after sintering. In this embodiment, the conductive paste is silver paste, Figure 9 (a) is a SEM image of the contact interface between the conductive paste and the N region 124 before sintering, and (b) is a SEM image of the contact interface between the conductive gate line 152 and the N region 124 formed after sintering. Figure 9 (a), Figure 9 (b) After sintering, the metal particles are more tightly bonded and in contact with each other, the conductive gate line 152 structure is more dense and uniform, the contact interface between the conductive gate line 152 and the N region 124 is also flatter and smoother, and the contact resistivity is significantly reduced, thereby optimizing the transmission path of charge carriers.

[0177] Table 1 Statistical table of contact resistivity of conductive paste in BC solar cells after sintering with N and P regions to form ohmic contact

[0178] Serial number <![CDATA[N-region contact resistivity / mΩ·cm 2 > <![CDATA[P-region contact resistivity / mΩ·cm 2 > 1 0.90 1.30 2 0.85 0.98 3 0.63 0.84 4 0.46 0.65

[0179] The statistical data in Table 1 show that after sintering, four points of the conductive gate line in the N region and the P region were selected for testing. The average contact resistance at the interface between the conductive gate line 152 and the N region 124 was 0.71 mΩcm. 2 , and the average contact resistance at the interface with the P region 125 is 0.94mΩΩcm 2 .

[0180] In summary, after the above-mentioned electric sintering process, the line resistivity of the conductive grid line 152 does not exceed 1.0×10 -7Ω·m, compared with the existing tunnel furnace sintering or tunnel furnace sintering + laser induced sintering, the resistivity and contact resistivity of the conductive grid lines obtained can reach the same level in the industry. In addition, the characteristics of electric sintering such as good thermal field uniformity, low damage, and easy controllability can significantly improve the processing efficiency and yield of solar cells.

[0181] The solar cell preparation method provided in the present application has the following advantages over other existing sintering processes: 1. The heat of electric sintering is more concentrated, so that the conductive paste is heated as a whole, and a temperature gradient field with decreasing temperature from the outside to the inside similar to that generated by laser sintering will not be formed inside it; 2. Only the conductive paste that is energized generates heat, and the heat is relatively less likely to overflow, avoiding damage to other functional layers that are not resistant to high temperatures; 3. By adjusting the current or voltage and the power-on time, the sintering process and the final sintering temperature can be precisely controlled, which is beneficial to improving the microstructure and performance of the conductive paste and the contact interface; 4. In the electric sintering method, heat is transferred from the inside of the conductive paste to the outside, and the time that the outer layer of the conductive paste is in contact with the air is extremely short, which can greatly reduce the oxidation of the conductive grid line. 5. The uneven conductive paste can be reinforced at weak locations, so that the conductive paste at the weak locations can be supplemented to a certain extent, thereby achieving reinforced sintering of the weak high-resistance areas; in addition, the solar cell preparation method provided by the present application has high sintering efficiency, fast sintering speed, and is more compatible with base metal paste, and is extremely suitable for the sintering of base metal paste, and can avoid oxidation of the base metal paste during the sintering process (such as copper paste oxidation); it is also suitable for the design of a main grid electrode, and provides a good industrialization method for further reducing the cost of manufacturing conductive grid lines using metal paste.

[0182] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: include: Providing a semi-finished solar cell having a conductive paste formed in a predetermined area of ​​a solar cell substrate; The conductive paste is electrified to electrically sinter the conductive paste, so that the conductive paste forms conductive grid lines on solar cells.

2. The method for preparing a solar cell according to claim 1, wherein: Before electrifying the conductive paste, the method further comprises: The semi-finished solar cell is dried.

3. The method for preparing a solar cell according to claim 1 or 2, wherein: The process parameters of the electric sintering include: the current density is 0.1mA / um 2 Above, the cumulative power-on time is greater than 0.1s.

4. The method for preparing a solar cell according to claim 1 or 2, characterized in that: The process parameters of the electric sintering include: using direct current, the current intensity of the direct current is less than 100A, and the cumulative power-on time is greater than 0.1s; or using pulse current, the pulse current amplitude is less than 10000A, the cumulative power-on time is greater than 0.1s, the pulse frequency is 10Hz~1000000Hz, and the duty cycle is 0.1~1.

5. The method for preparing a solar cell according to claim 1, wherein: The step of electrifying the conductive paste comprises: First, the conductive paste is electrified in a constant voltage mode; In response to the current flowing through the conductive paste reaching a preset current value, the constant voltage mode is switched to a constant current mode to maintain the preset current value continuously flowing through the conductive paste.

6. The method for preparing a solar cell according to claim 1, wherein: The electrifying the conductive paste comprises: After electrification is applied to both ends of any continuous line of the conductive paste, the continuous line with electrification at both ends has a potential difference, and is electrically sintered under the action of the potential difference.

7. The method for preparing a solar cell according to claim 1, wherein: The electrifying the conductive paste comprises: The conductive paste is electrified in multiple steps, and the process parameters of each step of the electrification sintering are the same or different.

8. The method for preparing a solar cell according to claim 1, wherein: The electrifying the conductive paste includes: the number of electrified contact points of any continuous line in the conductive paste is 3 or more.

9. The method for preparing a solar cell according to any one of claims 1 to 8, characterized in that: After the step of electrically sintering the conductive paste, the method further comprises: Laser induced sintering is performed on the conductive grid lines to improve the electrical contact performance between the conductive grid lines and the solar cell substrate.

10. The method for preparing a solar cell according to claim 1, wherein: The conductive paste is silver paste or silver-coated copper paste. After sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -7 Ω·m.

11. The method for preparing a solar cell according to claim 1, wherein: The conductive paste is copper paste, aluminum paste or nickel paste. After sintering, the line resistivity of the conductive grid line does not exceed 1.0×10 -6 Ω·m.

12. The method for preparing a solar cell according to claim 1, wherein: The contact resistance between the conductive grid line and the solar cell substrate is no more than 10 mΩ·cm 2 .

13. The method for preparing a solar cell according to claim 1, wherein: The solar cell substrate includes a conductive layer or a doped layer, and the preset area is located on the conductive layer or the doped layer.

14. The method for preparing a solar cell according to claim 13, wherein: The conductive layer is a transparent oxide layer or a metal electrode layer.

15. A method for preparing a solar cell, characterized in that: include: Providing a semi-finished solar cell having a conductive paste formed in a preset area of ​​a metal seed layer; The metal seed layer is electrified so that the conductive paste forms a conductive grid line.

16. The method for preparing a solar cell according to claim 15, wherein: The process parameters of the electric sintering include: the current density is 0.1mA / um 2 Above, the cumulative power-on time is greater than 0.1s.

17. A solar cell, characterized in that: The solar cell is prepared by the method for preparing the solar cell according to any one of claims 1 to 16.

Images