Drying device

Abstract

The utility model discloses a drying device which comprises a shell, a drying cavity is formed in the shell, and the drying cavity comprises a first cavity body and a second cavity body which are sequentially arranged in the first direction; the conveying belt comprises a bearing surface; the microwave generating mechanism is arranged in the second cavity and comprises a microwave irradiation end facing the bearing surface so as to form an irradiation area on the bearing surface; the heating mechanism is arranged in the first cavity and comprises an operation end facing the bearing face. The heating mechanism and the microwave generating mechanism are arranged in the drying cavity, the heating mechanism heats each layer of the battery piece to the consistent temperature, and the microwave generating mechanism performs microwave treatment on the conductive slurry, so that sufficient volatilization of moisture and organic matters in each part of the conductive slurry can be ensured, and organic matter residues are avoided; the contact resistance and the line resistance of the grid line electrode are optimized, the filling factor and the open-circuit voltage are improved, and the efficiency of the battery piece is improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to solar cell technical field, specifically about a drying device. BACKGROUND

[0002] The grid electrode of a solar cell is a key structure for collecting photo-generated current on the surface of the cell, which is generally prepared by the steps of screen printing paste, drying and sintering. The purpose of drying is to remove organic solvents and tar in the paste, so that the paste is solidified into a film and tightly attached to the surface of the silicon wafer.

[0003] In the existing solar cell preparation process, the drying method of the paste is surface heating, and the heat is transmitted from the outside to the inside of the paste. The solidification speed of the outside and the inside of the paste is different, which is easy to cause the phenomenon that the shell of the paste is solidified but the inside is not completely solidified, which affects the volatilization effect of the organic matter in the conductive paste, and the residual organic matter will affect the efficiency of the battery piece. INVENTION CONTENTS

[0004] The purpose of the present application is to provide a drying device to solve the technical problem that the drying method of the paste in the prior art is easy to cause the phenomenon that the shell of the paste is solidified but the inside is not completely solidified, which affects the volatilization effect of the organic matter in the conductive paste, and the residual organic matter will affect the efficiency of the battery piece.

[0005] In order to achieve the above-mentioned purpose, the present application provides a drying device, comprising:

[0006] A shell is arranged inside a drying cavity, and the shell is provided with an inlet and an outlet at both ends, respectively. The drying cavity comprises a first cavity and a second cavity arranged in sequence along a first direction;

[0007] A conveyor belt is arranged to connect the inlet and the outlet along the first direction, and the conveyor belt comprises a bearing surface for bearing the battery piece;

[0008] A microwave generating mechanism is arranged in the second cavity, and the microwave generating mechanism comprises a microwave irradiation end facing the bearing surface to form a microwave irradiation area on the bearing surface;

[0009] A heating mechanism is arranged in the drying cavity, and the heating mechanism comprises a working end facing the bearing surface to form a heating area on the bearing surface, and the heating area overlaps with the microwave irradiation area or is located on the side of the microwave irradiation area close to the inlet;

[0010] Wherein, the first direction is the direction of the inlet pointing to the outlet

[0011] In one or more embodiments, the heating region has a length of extension in the first direction that is greater than a length of extension of the microwave irradiation region.

[0012] In one or more embodiments, the heating mechanism comprises one or more combinations of a metallic heating element, an infrared heating element, and an electromagnetic induction heating element.

[0013] In one or more embodiments, the drying device further comprises a heat insulation layer arranged between the heating mechanism and the housing.

[0014] In one or more embodiments, the conveyor belt comprises:

[0015] a plurality of drive rollers arranged in sequence and spaced apart along the first direction, the drive rollers extending along a second direction;

[0016] a plurality of insulating rollers arranged in sequence and spaced apart along the second direction on the drive rollers, the insulating rollers being configured to support the battery slices;

[0017] wherein the second direction is perpendicular to the first direction.

[0018] In one or more embodiments, the plurality of insulating rollers comprises a plurality of first rollers arranged at a middle portion of the drive rollers and a plurality of second rollers arranged close to both ends of the drive rollers, the positions of the second rollers on the drive rollers being adjustable.

[0019] In one or more embodiments, the drive rollers are arranged with a guide flat key extending along an axial direction thereof, the second rollers are arranged with a key groove matching the guide flat key, and the second rollers are arranged to be slidably disposed along the guide flat key, the second rollers are arranged with a fixing hole, and a fastening bolt is arranged in the fixing hole and configured to abut against the guide flat key.

[0020] In one or more embodiments, a limiting plate is arranged on a ring surface of the second roller away from one end of the first roller.

[0021] In one or more embodiments, the insulating rollers are ceramic rollers.

[0022] In one or more embodiments, the drying cavity further comprises a third cavity arranged close to one end of the discharge port, so as to form a cooling region for cooling the support surface in the third cavity.

[0023] In one or more embodiments, the drying cavity further comprises a fourth cavity between the first cavity and the second cavity, and the drying device further comprises a first microwave suppressor arranged in the fourth cavity.

[0024] In one or more embodiments, the drying cavity further comprises a fifth cavity located at one end of the second cavity close to the discharge port, and the drying device further comprises a second microwave inhibitor arranged in the fifth cavity.

[0025] In one or more embodiments, the drying cavity further comprises a sixth cavity located at one side of the second cavity close to the discharge port, and the drying device further comprises an ultraviolet irradiation mechanism arranged in the sixth cavity, the ultraviolet irradiation mechanism comprising an ultraviolet irradiation end arranged facing the bearing surface to form an ultraviolet irradiation area on the bearing surface.

[0026] In one or more embodiments, a shielding layer is further arranged between the microwave generating mechanism and the shell.

[0027] In one or more embodiments, an organic waste discharge system and a hot air discharge system are further arranged in sequence on one end of the shell close to the discharge port along the first direction, and the shell is arranged with a first exhaust port communicating the drying cavity and the organic waste discharge system, and a second exhaust port communicating the drying cavity and the hot air discharge system.

[0028] In one or more embodiments, the shell further comprises an air inlet arranged between the heating mechanism and the feeding port, and the drying device further comprises an air inlet system communicating with the air inlet, the air inlet system being used for introducing air and / or inert gas into the drying cavity through the air inlet.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] The heating mechanism and the microwave generating mechanism are arranged in sequence in the drying cavity of the drying device, the heating mechanism heats each layer structure of the battery piece to a consistent temperature, and the microwave generating mechanism is used for microwave treatment of the conductive paste, which can ensure sufficient volatilization of moisture and organic matter in each part of the conductive paste, effectively avoid the residue of organic matter, and thus avoid the generation of bubbles or pollution in the subsequent sintering process, so as to avoid electrode fracture or poor contact. The application can effectively optimize the contact resistance and line resistance of the grid line electrode, and is beneficial to improving the fill factor and open circuit voltage, and improving the efficiency of the battery piece. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0032] Figure 1 is a structural schematic diagram of an embodiment of the drying device of the present application;

[0033] Figure 2 is a structural schematic diagram of an embodiment of the drying device of the present application; Figure 1 is a sectional structural schematic diagram of A-A in

[0034] Figure 3 is a structural schematic diagram of another embodiment of the drying device of the present application;

[0035] Figure 4 is a structural schematic diagram of still another embodiment of the drying device of the present application;

[0036] Figure 5 is a structural schematic diagram of still another embodiment of the drying device of the present application;

[0037] Figure 6 is an SEM image of the grid line electrode of the battery piece in Example 1 of the present application;

[0038] Figure 7 is an SEM image of the grid line electrode of the battery piece in Comparative Example 1 of the present application;

[0039] Figure 8 is a data graph of the photoelectric conversion efficiency of the battery pieces in Example 1 and Comparative Example 1;

[0040] Figure 9 is a data graph of the fill factor FF of the battery pieces in Example 1 and Comparative Example 1 of the present application;

[0041] Figure 10 is a box plot of the contact resistance Rc of the front grid line electrode of the battery pieces in Example 1 and Comparative Example 1;

[0042] Figure 11 is a data graph of the total series resistance Rs of the battery pieces in Example 1 and Comparative Example 1 of the present application.

[0043] Main reference signs:

[0044] housing 100; drying cavity 101; first cavity 1011; second cavity 1012; third cavity 1013; fourth cavity 1014; fifth cavity 1015; sixth cavity 1016; feeding port 102; discharging port 103; first exhaust port 104; second exhaust port 105; air inlet 106; heat preservation layer 107; shielding layer 108;

[0045] Conveying belt 200; bearing surface 201; heating area 2011; microwave irradiation area 2012; cooling area 2013; ultraviolet light irradiation area 2014; transmission roller 202; guide flat key 2021; insulating roller 203; first roller 2031; second roller 2032; fixing hole 2033; fastening bolt 2034; limiting plate 2035; key groove 2036;

[0046] Heating mechanism 300; infrared heating pipe 301;

[0047] Microwave generating mechanism 400;

[0048] Organic waste discharge system 500;

[0049] Hot air discharge system 600;

[0050] Air inlet system 700;

[0051] First microwave suppressor 800;

[0052] Second microwave suppressor 900;

[0053] Ultraviolet light irradiation mechanism 1000; UVA lamp tube 1001. DETAILED DESCRIPTION

[0054] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0055] The grid line electrode on the battery piece is generally prepared by screen printing, drying and sintering processes. Among them, the purpose of drying is to remove the organic solvent and tar in the grid paste, so that the paste is solidified into a film and tightly attached to the surface of the silicon wafer; the purpose of sintering is to establish ohmic contact between metal particles and silicon matrix at high temperature, to reduce the contact resistance between the electrode and the silicon wafer, and to optimize the carrier collection efficiency.

[0056] At present, the drying method of the grid paste all belongs to surface heating, and the heat is transmitted from the outside of the paste to the inside, resulting in different solidification speeds of the outside and the inside of the conductive paste, and the phenomenon that the conductive paste shell is solidified but the inside is not completely solidified, which affects the volatilization effect of the organic matter in the conductive paste. The residual organic matter will decompose and produce bubbles or pollution during subsequent high-temperature sintering, resulting in electrode fracture or poor contact, affecting the battery efficiency.

[0057] In order to solve the above problems, the applicant develops a new type of drying device which is applied to drying of conductive paste on the surface of battery piece, can ensure that the solidification rate of paste everywhere is consistent, thereby effectively avoiding the residue of organic matter and improving the battery efficiency.

[0058] Specifically, refer to Figure 1 , Figure 1 is a structural schematic diagram of an embodiment of the drying device of the present application.

[0059] As Figure 1 shown, the drying device includes a shell 100, the inside of the shell 100 is hollow to form a drying cavity 101, and the two ends of the shell 100 are respectively provided with a feeding port 102 for introducing the battery piece into the drying cavity 101 and a discharging port 103 for discharging the battery piece out of the drying cavity 101.

[0060] In order to facilitate the conveying of the battery piece, the drying device further includes a conveying belt 200 which is arranged to extend through the drying cavity 101 along a first direction X and is connected to the feeding port 102 and the discharging port 103, and the conveying belt 200 includes a bearing surface 201 for bearing the battery piece.

[0061] In the embodiment, the drying cavity 101 includes a first cavity 1011 and a second cavity 1012 which are arranged in sequence along the first direction X, wherein the first cavity 1011 is internally arranged with a heating mechanism 300 which includes a working end arranged to face the bearing surface 201 to form a heating area 2011 on the bearing surface 201; and the second cavity 1012 is internally arranged with a microwave generating mechanism 400 which includes a microwave irradiation end arranged to face the bearing surface 201 to form a microwave irradiation area 2012 on the bearing surface 201.

[0062] By placing the battery piece on the bearing surface 201 of the conveying belt 200, the battery piece can pass through the heating area 2011 and the microwave irradiation area 2012 in sequence under the conveying action of the conveying belt 200.

[0063] In the microwave irradiation area 2012, the conductive paste on the surface of the battery piece is solidified by the microwave heating treatment output by the microwave generating mechanism 400. Since the microwave treatment is volumetric heating and does not require a heat transfer medium, the inside and outside of the conductive paste can be heated at the same time, which helps to volatilize the moisture and organic matter and avoids the situation that the paste is dried on the outside but not on the inside, thereby effectively avoiding the residue of organic matter, reducing the resistance, and improving the filling factor and battery efficiency.

[0064] Among them, the microwave generating mechanism 400 can be any element capable of generating microwave energy, such as a transistor microwave generator, a microwave photon generator, a solid-state microwave generator, etc., all of which can achieve the effect of the embodiment.

[0065] Since the battery piece is a multi-layer structure including a silicon substrate, a passivation layer, and a paste, etc., the dielectric properties of different materials are inconsistent, and the absorption effect of microwaves is inconsistent. If a single microwave treatment is used, there will be a problem of inconsistent temperature of the silicon substrate and the paste, and due to the difference in the thermal expansion coefficient of the material, the grid line will crack and fall off, and due to the local temperature unevenness of the silicon wafer, the wafer will crack.

[0066] Therefore, in the present embodiment, the drying device further comprises a heating mechanism 300. In the heating area 2011, the temperature of each layer structure of the silicon substrate, the conductive paste, and the passivation layer of the battery piece can be preheated to be consistent, thereby effectively avoiding the problems of grid line cracking, falling off, and wafer cracking caused by the difference in the thermal expansion coefficient of the material during subsequent microwave treatment, and improving the heating uniformity.

[0067] Specifically, in the present embodiment, the heating mechanism 300 comprises a plurality of infrared heating pipes 301 arranged in the first direction X in sequence. The infrared heating pipe 301 can be arranged in a direction perpendicular to the first direction X to ensure the heating uniformity. Infrared heating has higher thermal efficiency and heating rate. By assisting microwave heating with infrared heating, the temperature can be monitored and the temperature curve can be adjusted by the temperature control module, so as to avoid uneven stress distribution of the grid electrode and the silicon substrate caused by the thermal expansion coefficient problem.

[0068] Of course, in other embodiments, the heating mechanism 300 can also include a metal heating plate, or an electromagnetic induction heating pipe, or both a metal heating plate, an infrared heating pipe, and an electromagnetic induction heating pipe, etc., which can all achieve the effect of the present embodiment.

[0069] It should be noted that the purpose of the heating mechanism 300 in the present embodiment is to preheat each layer structure of the battery piece to the same temperature, so that the heating elements that can achieve this purpose can all achieve the effect of the present embodiment, and are not limited to the heating elements listed above.

[0070] In one embodiment, the heating temperature of the heating mechanism 300 can be 100-400°C, and the time for each part of the battery piece to be in the heating area 2011 can be less than or equal to 150s.

[0071] In one embodiment, the power of the microwave generating mechanism 400 can be 500-1500W. More preferably, the power of the microwave generating mechanism 400 can be 900W.

[0072] In one embodiment, the wavelength of the microwaves output by the microwave generating mechanism 400 can be 0.1-1m, and correspondingly, the frequency of the microwaves can be 300MHz-3GHz.

[0073] More specifically, the microwave frequency can be 433 MHz, 915 MHz or 2450 MHz.

[0074] In one embodiment, the time for each part of the battery piece to be in the microwave irradiation area 2012 can be 15-30 s.

[0075] It should be understood that the size of the microwave frequency, the processing time and the thickness of the conductive paste and other parameters are associated, high frequency microwave heating speed is fast, but the penetration depth is shallow, suitable for thin layer materials; while low frequency microwave has strong penetration, but the heating speed is slow, suitable for thicker materials. In specific implementation, the frequency of the microwave and the time for the battery piece to undergo microwave treatment can be adjusted based on the thickness of the conductive paste and other process parameters, and the complete curing of the conductive paste can be ensured, which can achieve the effect of the present embodiment.

[0076] In the present embodiment, the heating mechanism 300 and the microwave generating mechanism 400 are arranged at the top of the first cavity 1011 and the second cavity 1012, respectively. In other embodiments, the heating mechanism 300 and the microwave generating mechanism 400 can also be arranged at other positions of the first cavity 1011 and the second cavity 1012, such as the side wall, the bottom, etc. of the cavity, which can achieve the heating and curing of the conductive paste on the surface of the battery piece on the carrying surface 201, and can achieve the effect of the present embodiment.

[0077] In the present embodiment, the battery piece can be any substrate and epitaxial assembly of a solar cell in the art that needs to arrange a grid line electrode or a back field, for example, the solar cell can be an aluminum back field (aSF) battery piece, a PERC battery piece, a heterojunction (HJT) cell, a TOPCon cell, an IaC cell, etc., which can achieve the present embodiment.

[0078] The conductive paste can be any metal paste commonly used in the art, such as conductive silver paste, etc. The conductive paste can be arranged in a grid or mesh shape on the surface of the battery piece, or uniformly arranged on the surface of the battery piece, so as to form a grid line electrode or a back field for collecting photo-generated current after drying in the drying device and subsequent sintering process.

[0079] In order to ensure that the curing effect of the battery piece is consistent, the conveying belt 200 can maintain uniform motion, and each part of the battery piece can quickly undergo microwave treatment after completing the preheating treatment, avoiding heat loss, ensuring that the temperature of each layer is consistent during subsequent microwave treatment, and ensuring that the curing effect of each part of the battery piece is consistent.

[0080] When the conveying belt 200 keeps uniform motion, in order to control the time of each battery piece passing through the preheating and irradiation processes, the extension length b of the heating area 2011 in the first direction X and the motion speed v of the conveying belt 200 can satisfy the following formula: b / v≦150s, and the extension length a of the microwave irradiation area 2012 in the first direction X and the motion speed v of the conveying belt 200 satisfy the following formula: 15s≤a / v≤30s.

[0081] In the embodiment, the drying cavity 101 further comprises a third cavity 1013 arranged at one end close to the discharge port 103, and no heating element is arranged in the third cavity 1013, so as to form a cooling area 2013 for cooling the bearing surface 201 in the third cavity 1013.

[0082] The battery piece after the microwave treatment can be slowly cooled when passing through the cooling area 2013, and finally leave the drying cavity 101 through the discharge port 103, so as to avoid the problem of grid line electrode falling off due to too high temperature gradient when the battery piece directly leaves the drying cavity 101 after the microwave treatment.

[0083] In the embodiment, in order to avoid the heat overflow of the heating mechanism 300 and the microwave overflow of the microwave generating mechanism 400, the drying device further comprises a heat preservation layer 107 arranged between the heating mechanism 300 and the shell 100, and a shielding layer 108 arranged between the microwave generating mechanism 400 and the shell 100, so as to effectively isolate the drying cavity 101 from the external environment.

[0084] The conveying belt 200 of the traditional drying furnace adopts a mesh belt transmission, conveying wheels and tensioning wheels are arranged on both sides of the mesh belt to form a rotary track, the mesh belt is driven to move by the conveying wheels to drive the battery pieces on the surface of the mesh belt to move, and the mesh belt needs to reciprocate in and out of the cavity, and needs to be reheated when returning from outside the cavity to inside the cavity, which causes heat loss. In addition, ceramic limit blocks and metal rollers are arranged on both sides of the mesh belt as limit devices, and quartz rods are used as supports at the bottom, a large amount of grinding dust particles are generated during long-term operation, and regular cleaning and maintenance are required.

[0085] In order to solve the above problems, the conveying belt 200 in the embodiment comprises a plurality of transmission rollers 202 arranged in sequence and at intervals along the first direction X, the transmission rollers 202 are arranged in extension along a direction perpendicular to the first direction X, and a plurality of insulating rollers 203 are arranged on the transmission rollers 202, the plurality of insulating rollers 203 are arranged in sequence and at intervals on the transmission rollers 202 along the axial direction of the transmission rollers 202, and the insulating rollers 203 are used to support the battery pieces. The transmission rollers 202 can be driven to rotate by any rotating driving element commonly used in the art, so as to drive the insulating rollers 203 to rotate for battery piece conveying.

[0086] Based on the structure of the conveying belt 200, the transmission roller 202 and the insulating roller 203 are always located in the drying cavity 101, effectively avoiding the heat loss caused by the reciprocating motion of the mesh belt in and out of the cavity in the traditional drying furnace; at the same time, there is no need to set the bottom support, avoiding the problem of grinding dust particles caused by long-term operation.

[0087] In one embodiment, the material of the insulating roller 203 can be ceramic. Ceramic is an insulating material that does not absorb and reflect microwaves, ensuring the uniformity of microwave distribution and reducing the risk of partial discharge. At the same time, the high temperature resistance and chemical stability of ceramic are suitable for high temperature environment. Of course, in other embodiments, the insulating roller 203 can also use other materials that meet the requirements of insulation, high temperature resistance and chemical stability, which can achieve the effect of the present embodiment.

[0088] In order to ensure that each part of the battery piece is fully supported, and at the same time meet the needs of battery pieces of different sizes, please refer to Figure 2 , Figure 2 is Figure 1 the cross-sectional structure schematic diagram of A-A plane.

[0089] As shown in Figure 2 , in the present embodiment, four insulating rollers 203 are arranged on the transmission roller 202, including two first rollers 2031 located in the middle of the transmission roller 202 and two second rollers 2032 close to the two ends of the transmission roller 202. The first roller 2031 and the second roller 2032 can cooperate to stably support each part of the battery piece.

[0090] In order to make the conveying belt 200 adapt to battery pieces of different sizes, the position of the second roller 2032 on the conveying roller can be adjusted. Specifically, in the present embodiment, a guide flat key 2021 extending along the axial direction of the transmission roller 202 is arranged on the transmission roller 202, and the second roller 2032 is arranged with a key groove 2036 matched with the guide flat key 2021, and the second roller 2032 can be slidably arranged along the guide flat key 2021.

[0091] The second roller 2032 is arranged with a fixing hole 2033, and a fastening bolt 2034 capable of abutting and fixing with the guide flat key 2021 is arranged in the fixing hole 2033. The position adjustment of the second roller 2032 can be realized by the cooperation of the fastening bolt 2034 and the guide flat key 2021, so as to meet the needs of battery pieces of different sizes.

[0092] Of course, in other embodiments, the second roller 2032 can also be connected with the transmission roller 202 in other ways, such as arranging screw holes directly on the transmission roller 202, adjusting the screw holes fixed with the second roller 2032 to realize the fixation of the second roller 2032, etc., which can realize the effect of the present embodiment, and will not be repeated here.

[0093] In addition, in the embodiment, only the position of the second roller 2032 is adjustable, and in other embodiments, the position of the first roller 2031 on the transmission roller 202 can also be adjustably arranged, so as to adjust the supporting position of the first roller 2031 for battery pieces of different sizes, and further improve the conveying stability of the battery pieces.

[0094] Further, as shown in Figure 2 In the embodiment, the annular surface of the second roller 2032 away from the first roller 2031 is arranged with a limiting plate 2035, so that the pair of limiting plates 2035 can limit the battery pieces in a direction perpendicular to the first direction X, further improving the conveying stability of the battery pieces.

[0095] Please continue to refer to Figure 1 In the embodiment, the drying device further comprises an organic waste discharge system 500 and a hot air discharge system 600, which are arranged in sequence on one end of the shell 100 close to the discharge port 103 along the first direction X.

[0096] The shell 100 is arranged with a first exhaust port 104 communicating the drying cavity 101 and the organic waste discharge system 500, and a second exhaust port 105 communicating the drying cavity 101 and the hot air discharge system 600.

[0097] The VOCs volatilized in the process of drying the conductive paste are collected and treated by the organic waste discharge system 500 and discharged, and the heat in the drying process is recovered by the hot air discharge system 600, reducing energy consumption.

[0098] Further, in the embodiment, the organic waste discharge system 500 and the hot air discharge system 600 are arranged in sequence on the shell 100 along the first direction X, so as to effectively prevent VOCs from entering the hot air discharge system 600.

[0099] In addition, in the embodiment, the first exhaust port 104 and the second exhaust port 105 are arranged in communication with the third cavity 1013, so as to form an airflow moving along the first direction X in the drying cavity 101, ensuring that the organic matter and heat can be effectively recovered and discharged by the organic waste discharge system 500 and the hot air discharge system 600. In other embodiments, the first exhaust port 104 and the second exhaust port 105 can also be arranged at other positions, such as the second cavity 1012, etc., as long as the sufficient recovery and discharge of the organic matter and heat can be realized.

[0100] In the above embodiments, the second cavity 1012 is in an air atmosphere, and the conductive paste is subjected to microwave treatment in the air atmosphere. In another embodiment, the second cavity 1012 can also be in an inert atmosphere, and the conductive paste is subjected to microwave treatment in the inert atmosphere, so as to effectively avoid the generation of electric arc.

[0101] Specifically, referring to Figure 3 , Figure 3 is a structural schematic diagram of another embodiment of the drying device.

[0102] As Figure 3 shown, the shell 100 further comprises an air inlet 106 arranged between the heating mechanism 300 and the feeding port 102, and the drying device further comprises an air inlet system 700 in communication with the air inlet 106. The air inlet system 700 can comprise an inert gas source and an air inlet pipe connected between the inert gas source and the air inlet 106, so that the inert gas can be introduced into the drying cavity 101 through the air inlet 106. Under the exhaust action of the organic waste discharge system 500 and the hot air discharge system 600, the second cavity 1012 can be in an inert atmosphere, so as to effectively avoid the generation of electric arc.

[0103] The inert gas can be nitrogen, argon or the like, and all of them can achieve the effect of the embodiment.

[0104] In an embodiment, the inert gas can be preheated before being introduced into the drying cavity 101, so as to avoid affecting the drying effect of the conductive paste.

[0105] Of course, in the embodiment shown in Figure 3 , the air inlet system 700 can also be used to introduce air into the drying cavity 101. The air can be preheated before being introduced into the drying cavity 101, so as to avoid affecting the drying effect of the conductive paste.

[0106] In the above embodiments, the heating mechanism 300 and the microwave generating mechanism 400 are arranged adjacent to each other, and there can be mutual interference problems between them. For example, when the heating mechanism 300 is an infrared heating pipe 301, the infrared heating pipe 301 will absorb microwaves, resulting in uneven distribution of microwaves and low energy utilization rate.

[0107] In order to solve the above problems, referring to Figure 4 , Figure 4 is a structural schematic diagram of another embodiment of the drying device.

[0108] As Figure 4As shown, the drying cavity 101 further comprises a fourth cavity 1014 arranged between the first cavity 1011 and the second cavity 1012, and the drying device further comprises a first microwave inhibitor 800 arranged in the fourth cavity 1014. Through the uniform action of the microwave of the first microwave inhibitor 800, the mutual interference between the heating mechanism 300 and the microwave generating mechanism 400 can be effectively avoided, the uniform distribution of the microwave is ensured, and the energy utilization rate is improved.

[0109] Further, in the embodiment, the drying cavity 101 further comprises a fifth cavity 1015 located at one end of the second cavity 1012 close to the discharge port 103, and the drying device further comprises a second microwave inhibitor 900 arranged in the fifth cavity 1015, so as to further avoid the harm of microwave leakage to the health of the operator, while ensuring the uniform distribution of the microwave.

[0110] Based on the drying device of each of the above embodiments, in a first aspect, the drying of the conductive paste is carried out through the auxiliary microwave treatment of the heating treatment. The microwave treatment can ensure the volatilization effect of the moisture and organic matter of each part of the conductive paste, reduce the grid line resistance, and improve the filling factor. The heating treatment can avoid the problem of inconsistent temperature of each part of the battery piece caused by the microwave treatment, avoid the problems of grid line cracking, falling off and cracking caused by the difference in thermal expansion coefficient of the material, and improve the heating uniformity.

[0111] In a second aspect, the conveyor belt 200 composed of the transmission roller 202 and the insulating roller 203 can effectively avoid the heat loss caused by the reciprocating motion of the mesh belt in the cavity and outside the cavity in the rotary track composed of the mesh belt, the transmission roller and the tensioning roller in the traditional drying furnace, and avoid the problem of grinding dust particles caused by long-term operation. At the same time, the position of the insulating roller 203 at the end is adjustable, which can meet the demand of battery pieces of different sizes and is compatible with the production and preparation of silicon pieces of 156-210 sizes in the market.

[0112] In a third aspect, in the traditional metal heating drying furnace and infrared heating drying furnace, the metal heating pipe and the infrared heating pipe are arranged in a penetrating cavity manner, which has the disadvantages of light leakage and poor cavity heat preservation. Through the microwave drying of the conductive paste by the microwave generating mechanism 400, the disadvantages can be effectively avoided.

[0113] In a fourth aspect, since the microwave heating has the advantages of fast starting speed and direct action on the object without relying on the medium to transmit heat energy, the energy consumption is significantly lower than that of the existing resistance heating and infrared heating, and the heating efficiency is also higher.

[0114] In each of the above embodiments, the battery piece sequentially passes through the heating region 2011 and the microwave irradiation region 2012 to realize solidification. In another embodiment, considering that the surface of the conductive paste after solidification by the microwave treatment may have surface defects, the drying device can further comprise an ultraviolet light irradiation mechanism 1000. Specifically, please refer to Figure 5 ,Figure 5 is a structural schematic diagram of another embodiment of the drying device.

[0115] As shown in Figure 5 , the drying cavity in this embodiment further includes a sixth cavity 1016 located on the side of the second cavity 1012 close to the discharge port 103, and the drying device further includes an ultraviolet light irradiation mechanism 1000 arranged in the sixth cavity 1016.

[0116] The ultraviolet light irradiation mechanism 1000 includes an ultraviolet irradiation end facing the bearing surface 201 to form an ultraviolet light irradiation area 2014 on the bearing surface 201.

[0117] In this embodiment, the ultraviolet light irradiation mechanism 1000 includes a plurality of UVA lamp tubes 1001 arranged above and below the conveying belt 200 in the first direction x; in other embodiments, other mechanisms capable of irradiating ultraviolet light can also be used to achieve the effects of this embodiment.

[0118] In one embodiment, the ultraviolet light irradiated by the ultraviolet light irradiation mechanism 1000 can be UVA, and the wavelength of the ultraviolet light is 315nm-400nm.

[0119] In one embodiment, the residence time of the battery piece in the ultraviolet light irradiation area 2014 can be less than or equal to 5s.

[0120] The surface defects of the conductive paste after drying are key problems affecting its conductive performance and subsequent application. In order to eliminate the surface defects of the conductive paste after drying, the ultraviolet light irradiation mechanism 1000 is also arranged in the drying device in this embodiment, and the conductive paste after microwave treatment is also subjected to ultraviolet light irradiation treatment. Through ultraviolet light injection, the surface defects generated during the curing process of the conductive paste can be activated and repaired, the surface recombination rate is reduced, and the open circuit voltage is improved.

[0121] The effects of the technical solutions of the present application will be further described in detail below in conjunction with specific embodiments.

[0122] Embodiment 1:

[0123] A battery piece is prepared by the following steps:

[0124] The conductive silver paste is printed on the front and back surfaces of the battery piece in steps, and the conductive silver paste is subjected to a drying process after each printing. After the last drying is completed, the electrode piece is subjected to a sintering process.

[0125] The drying process uses a drying device. Figure 4The drying device shown, the heating mechanism in the drying device is an infrared heating tube, the heating temperature is 120 DEG C, the residence time of the battery piece in the heating area is 120s, the power of the microwave generating mechanism is 900W, the microwave frequency is 2450MHz, and the residence time of the battery piece in the microwave irradiation area is 20s.

[0126] Comparative Example 1

[0127] A battery piece, the preparation method is basically the same as that of Example 1, except that:

[0128] The drying process of Comparative Example 1 uses a traditional drying furnace, which has an infrared heating tube built-in. The battery piece passes through the action area of the infrared heating tube at a uniform speed under the action of the conveyor belt. The battery piece is subjected to infrared heating treatment to dry the conductive silver paste. The heating temperature of the infrared heating treatment is 200-300 DEG C, the temperature gradient increases, and the total heating time is 17s.

[0129] Characterization analysis:

[0130] The grid line electrodes of the battery pieces prepared by Example 1 and Comparative Example 1 are characterized and analyzed, and the following results are obtained: Figure 6 and Figure 7 , Figure 6 is the SEM image of the grid line electrode of the battery piece in Example 1 of the application, Figure 7 is the SEM image of the grid line electrode of the battery piece in Comparative Example 1 of the application.

[0131] As shown in Figure 7 , there are many bubbles in the grid line electrode of Comparative Example 1, which can easily lead to poor electrode contact. This is mainly due to incomplete volatilization of the internal organic matter during the drying process of the conductive silver paste in Comparative Example 1, and the residual organic matter decomposes to produce bubbles in the subsequent sintering process.

[0132] As shown in Figure 6 , there are no bubbles in the grid line electrode of the battery piece of Example 1, and the compactness is higher.

[0133] The above data proves that the drying method of Example 1 can effectively avoid the residual of organic matter and ensure the complete solidification of the conductive silver paste everywhere.

[0134] Electrical performance analysis:

[0135] Battery pieces were prepared by the methods of Example 1 and Comparative Example 1 on different dates, respectively, and their photoelectric conversion efficiency, i.e. etb parameter, was measured and calculated, and the following results were obtained: Figure 8 , Figure 8 is the photoelectric conversion efficiency data graph of the battery pieces of Example 1 and Comparative Example 1.

[0136] As shown in Figure 8As shown, the photoelectric conversion efficiency of the solar cell in Example 1 is significantly better than that of Comparative Example 1. The average photoelectric conversion efficiency of the solar cell in Example 1 is 26.46%, which is 0.34% higher than that of Comparative Example 1.

[0137] Furthermore, the formula for calculating the cell efficiency of a solar cell is as follows:

[0138]

[0139] In the formula, η is the battery efficiency, and P in V is the incident light power. OC J is the open-circuit voltage. SC Where is the short-circuit current density, and FF is the fill factor.

[0140] Among them, V OC *J SC =P max P max The fill factor FF represents the battery's maximum output power; therefore, the larger the fill factor FF, the higher the battery efficiency.

[0141] Therefore, we prepared solar cells on different dates using the methods of Example 1 and Comparative Example 1, and measured and calculated the fill factor FF of the solar cells of Example 1 and Comparative Example 1, obtaining... Figure 9 data, Figure 9 This is a graph showing the fill factor FF data of the battery cells in Embodiment 1 and Comparative Example 1 of this application.

[0142] like Figure 9 As shown, the fill factor FF of the solar cell in Example 1 is significantly higher than that in Comparative Example 1. The fill factor FF of the solar cell in Example 1 increased by a maximum of 0.58% compared to Comparative Example 1.

[0143] Furthermore, the relationship between the fill factor FF and the total series resistance Rs of the solar cell is as follows:

[0144]

[0145] The total series resistance Rs includes the contact resistance Rc of the gate electrode. Therefore, the smaller the contact resistance Rc of the gate electrode, the larger the fill factor FF.

[0146] To this end, the applicant prepared battery cells on different dates using the methods of Example 1 and Comparative Example 1, and measured the contact resistance Rc of the front grid electrodes, obtaining... Figure 10 , Figure 10 This is a box plot of the contact resistance Rc of the front grid line electrode of the solar cell in Example 1 and Comparative Example 1.

[0147] like Figure 10As shown, the contact resistance Rc of the front grid line electrode of the battery cell of Example 1 is significantly lower than that of Comparative Example 1. Specifically, the median contact resistance Rc of the front grid line electrode of the battery cell of Example 1 is reduced by 34.35% compared to Comparative Example 1.

[0148] Furthermore, the applicant also measured the total series resistance Rs of the battery cells in Example 1 and Comparative Example 1, and obtained... Figure 11 , Figure 11 This is a data graph showing the total series resistance Rs of the battery cells in Embodiment 1 and Comparative Example 1 of this application.

[0149] like Figure 11 As shown, the total series resistance Rs of the solar cell in Example 1 is significantly lower than that in Comparative Example 1, and the average value of the total series resistance RS of the solar cell in Example 1 is reduced by 4.17% compared to Comparative Example 1.

[0150] The data above show that the cell of Example 1 has a higher fill factor FF, lower grid electrode contact resistance Rc and total series resistance RS compared to Comparative Example 1, and has better cell efficiency.

[0151] Example of effect 3:

[0152] The fabrication efficiency and energy consumption of the solar cells in Example 1 and Comparative Example 1 were calculated, and the results show that:

[0153] The fabrication efficiency of the solar cell in Example 1 was improved by at least 0.09% compared to Comparative Example 1, and the energy consumption was reduced by at least 10%.

[0154] Therefore, the drying device of Example 1 has higher efficiency and lower energy consumption because microwave heating has the advantages of fast start-up speed, direct action on objects, and no need to rely on a medium to transfer heat energy. Therefore, its energy consumption is significantly lower than that of existing resistance heating and infrared heating, and its heating efficiency is also higher.

[0155] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0156] Furthermore, it should be understood that although the description above refers to particular embodiments, the description is illustrative only and is not intended to limit the claimed invention. The disclosed embodiments are not meant to be limiting by any means, but merely to illustrate the generality of the claimed invention. The skilled person will understand that the claimed invention is not limited to the details of the above-described embodiments, but that other embodiments can be realized without departing from the spirit or essential characteristics of the claimed invention. The scope of the claimed invention is defined by the appended claims and their equivalents.

[0157] It will be apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Thus, the present embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present application should be determined by reasonable interpretation of the appended claims and their equivalents, and therefore it is intended that all changes therein be within the scope of the present application. Any reference signs in the claims should not be construed as limiting the scope of the claims.

[0158] Furthermore, it should be understood that although the description above refers to particular embodiments, the description is illustrative only and is not intended to limit the claimed invention. The disclosed embodiments are not meant to be limiting by any means, but merely to illustrate the generality of the claimed invention. The skilled person will understand that the claimed invention is not limited to the details of the above-described embodiments, but that other embodiments can be realized without departing from the spirit or essential characteristics of the claimed invention. The scope of the claimed invention is defined by the appended claims and their equivalents.

Claims

1. A drying apparatus, characterized in that, include: The shell has a drying chamber inside, and the shell has an inlet and an outlet at both ends. The drying chamber includes a first chamber and a second chamber arranged sequentially along a first direction. A conveyor belt extends along the first direction and connects the inlet and outlet. The conveyor belt includes a support surface for carrying the battery cells. A microwave generating mechanism is arranged in the second cavity, the microwave generating mechanism including a microwave irradiation end facing the bearing surface to form a microwave irradiation area on the bearing surface; A heating mechanism is arranged in the first cavity. The heating mechanism includes a working end facing the bearing surface to form a heating area on the bearing surface. The heating area is located on the side of the microwave irradiation area near the feed inlet. Wherein, the first direction is the direction from the feed inlet to the discharge outlet.

2. The drying apparatus according to claim 1, characterized in that, In the first direction, the extension length of the heating region is greater than the extension length of the microwave irradiation region.

3. The drying apparatus according to claim 1, characterized in that, The heating mechanism includes one or more combinations of metal heating elements, infrared heating elements, and electromagnetic induction heating elements; and / or, The drying device also includes a heat insulation layer disposed between the heating mechanism and the housing.

4. The drying apparatus according to claim 1, characterized in that, The conveyor belt includes: Multiple drive rollers are arranged at intervals along the first direction, and the drive rollers extend along the second direction; Multiple insulating rollers are arranged sequentially on the drive roller along the second direction, and the insulating rollers are used to support the battery cells; The second direction is perpendicular to the first direction.

5. The drying apparatus according to claim 4, characterized in that, The plurality of insulating rollers includes several first rollers located in the middle of the drive roller and second rollers near both ends of the drive roller, the position of the second rollers on the drive roller being adjustable.

6. The drying apparatus according to claim 5, characterized in that, The transmission roller is provided with a guide key extending along its axial direction; the second roller is provided with a keyway that matches the guide key, and the second roller is slidable along the guide key; the second roller is provided with a fixing hole, and a fastening bolt that can abut against and fix to the guide key is arranged in the fixing hole; and / or, A limiting plate is arranged on the annular surface of the second roller opposite to the end of the first roller.

7. The drying apparatus according to claim 4, characterized in that, The insulating roller is a ceramic roller.

8. The drying apparatus according to claim 1, characterized in that, The drying chamber also includes a third chamber arranged near the discharge port to form a cooling area within the third chamber for cooling the bearing surface.

9. The drying apparatus according to claim 1, characterized in that, The drying chamber further includes a fourth chamber located between the first chamber and the second chamber, and the drying device further includes a first microwave suppressor disposed within the fourth chamber; and / or, The drying chamber further includes a fifth chamber located at the end of the second chamber near the discharge port, and the drying device further includes a second microwave suppressor arranged in the fifth chamber.

10. The drying apparatus according to claim 1, characterized in that, The drying chamber further includes a sixth chamber located on the side of the second chamber near the discharge port. The drying device also includes an ultraviolet irradiation mechanism arranged in the sixth chamber. The ultraviolet irradiation mechanism includes an ultraviolet irradiation end facing the bearing surface to form an ultraviolet irradiation area on the bearing surface.

11. The drying apparatus according to claim 1, characterized in that, The drying device also includes a shielding layer disposed between the microwave generating mechanism and the housing.

12. The drying apparatus according to claim 1, characterized in that, The drying device further includes an organic waste discharge system and a hot air discharge system, which are sequentially arranged along the first direction at one end of the shell near the discharge port. The shell is provided with a first exhaust port connecting the drying chamber and the organic waste discharge system, and a second exhaust port connecting the drying chamber and the hot air discharge system.

13. The drying apparatus according to claim 1, characterized in that, The housing also includes an air inlet disposed between the heating mechanism and the feed inlet, and the drying device also includes an air intake system communicating with the air inlet, the air intake system being used to introduce air and / or inert gas into the drying chamber through the air inlet.

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