Back-contact battery string and manufacturing method therefor, and photovoltaic assembly

Abstract

A back-contact battery string and a manufacturing method therefor, and a photovoltaic assembly. The back-contact battery string comprises several back-contact battery cells, wherein there is no metal electrode in each back-contact battery cell. The back-contact battery string further comprises a cured conductive adhesive and a busbar including a conductive layer, wherein the busbar is attached to the side of conductive film layers of the several back-contact battery cells by means of the conductive layer; the cured conductive adhesive is provided between the conductive layer and the conductive film layers; and when the area of a PN junction is 20-40 mm2, the thickness of the conductive layer is 10-50 μm, and when the area of the PN junction is 41-80 mm2, the thickness of the conductive layer is 51-100 μm. The back-contact battery string can realize the use of a back-contact battery cell without a metal electrode (i.e., without a main grid line), thereby reducing the electrode cost, reducing the current transmission step, reducing the power loss, and improving the battery string power.

Description

Back contact battery string, manufacturing method thereof, and photovoltaic module

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202410245884.0 filed with the Patent Office of China on March 5, 2024, entitled “A back-contact battery string, its manufacturing method, and photovoltaic module,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure belongs to the technical field of back-contact cells, and in particular relates to a back-contact cell string, a manufacturing method thereof, and a photovoltaic module. Background Art

[0004] At present, the N electrode and P electrode of the back-contact battery are both located on the back of the battery cell. The metal electrodes are usually made by low-temperature silver paste or copper electroplating, and then bonded or welded together through flexible plates, busbars or welding strips to achieve interconnection of corresponding electrodes between different batteries to form a battery string.

[0005] Prior art 1 uses an adhesive material with conductive particles to bond connecting components to corresponding electrodes of adjacent back contact cells to form a cell string and photovoltaic module. Prior art 2 uses a busbar to connect corresponding electrodes of different cells.

[0006] However, the above-mentioned methods of the prior art for connecting back-contact cells have the following disadvantages:

[0007] (1) The back contact cell requires a metal electrode (some include a fine gate electrode and a main gate electrode). The metal electrode is mostly realized by silver paste electrode or electroplated copper electrode, and the electrode cost is relatively high.

[0008] (2) The current is collected through metal electrodes and then connected to busbars, flexible plates, etc. for conduction, resulting in large power losses.

[0009] It should be noted that this part of the present disclosure only provides background technology related to the present disclosure and does not necessarily constitute prior art or public known technology.

[0010] Application Contents

[0011] The purpose of the present disclosure is to overcome the defects of the prior art in that metal electrodes need to be set when traditional back-contact cells form cell strings, which leads to high electrode costs and large power losses. A back-contact cell string, a manufacturing method thereof, and a photovoltaic module are provided. The back-contact cell string can realize the use of back-contact cells without metal electrodes (i.e., without main grid lines), thereby reducing electrode costs, reducing current transmission links, and reducing power losses. At the same time, the solidified conductive colloid can disperse the collected current and improve the power of the cell string.

[0012] To achieve the above objectives, in a first aspect, the present disclosure provides a back-contact cell string comprising a plurality of back-contact cell sheets. The back-contact cell sheet comprises a silicon wafer, an N-type conductive region and a P-type conductive region arranged on the back side of the silicon wafer and alternately distributed along the width direction of the back side, and an isolation region located between the N-type conductive region and the P-type conductive region. Conductive film layers are respectively provided on the outer surfaces of the N-type conductive region and the P-type conductive region. The conductive film layer comprises a transparent conductive film layer or a composite layer comprising a transparent conductive film layer and a metal conductive film layer. The silicon wafer and the corresponding conductive region having a different conductivity type from the silicon wafer form a PN junction. There are no metal electrodes in the back-contact cell sheet, and the back-contact cell string further comprises a solidified conductive colloid and a busbar comprising a conductive layer. The busbar is attached to one side of the conductive film layer of the plurality of back-contact cell sheets through the conductive layer, and the distribution pattern formed by the conductive layer on the busbar corresponds to and is aligned with the overall distribution pattern formed by the N-type conductive region and the P-type conductive region. The solidified conductive colloid is arranged between the conductive layer and the conductive film layer. The width of the conductive layer is between 1 / 3 and 1 times the width of the P-type conductive region. The PN junction area is 20-40 mm. 2 The thickness of the conductive layer is 10-50μm; the PN junction area is 41-80mm 2 The thickness of the conductive layer is 51-100 μm.

[0013] In some optional embodiments of the present disclosure, when the silicon wafer is N-type, the area of ​​the P-type conductive region is 20-40 mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the P-type conductive region is 41-80mm 2 When the silicon wafer is P-type, the thickness of the conductive layer is 51-100μm; when the silicon wafer is P-type, the area of ​​the N-type conductive area is 20-40mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the N-type conductive area is 41-80mm 2 The thickness of the conductive layer is 51-100 μm.

[0014] In some optional embodiments of the present disclosure, the volume resistivity of the cured conductive colloid is not higher than 7×10 -4 Ω·cm, optional not higher than 5×10 -4 Ω·cm, and / or the volume resistivity of the conductive layer is not higher than 1×10 -4 Ω·cm.

[0015] In some optional embodiments of the present disclosure, the cured conductive colloid includes conductive glue or solder paste.

[0016] Optionally, the conductive adhesive comprises a gelatin matrix and a conductive component, wherein the conductive component comprises a conductive metal and / or a conductive non-metal; and the content of the conductive component is 50-98 wt %.

[0017] Optionally, the conductive non-metal includes at least one of graphite, graphene and carbon nanotubes.

[0018] Optionally, the conductive metal is selected from at least one of gold, silver, indium, copper, tin, aluminum, zinc, iron and nickel.

[0019] In some optional embodiments of the present disclosure, the cured conductive colloid includes conductive glue, and the conductive film layer is a transparent conductive film layer.

[0020] In some optional embodiments of the present disclosure, the solidified conductive colloid comprises a conductive metal, wherein the conductive metal is a metal capable of forming an ohmic contact with the conductive film layer corresponding to each conductive region. Optionally, the conductive metal is selected from at least one of silver, indium, and tin.

[0021] In some optional embodiments of the present disclosure, the conductive component exists in a granular form.

[0022] In some optional embodiments of the present disclosure, the conductive adhesive further includes a dispersing additive and an optional auxiliary agent, wherein the dispersing additive is present in an amount of 1-30 wt % and the auxiliary agent is present in an amount of 0-10 wt %. Optionally, the dispersing additive includes at least one of acetone, methanol, ethanol, isopropyl alcohol, and butyl acetate. Optionally, the auxiliary agent includes at least one of a defoaming agent, a leveling agent, a flux, a diluent, and a curing agent.

[0023] In some optional embodiments of the present disclosure, the colloid matrix comprises resin.

[0024] Optionally, the resin includes at least one of epoxy resin, silicone resin, polyimide resin, phenolic resin, polyurethane and acrylic resin.

[0025] In some optional embodiments of the present disclosure, the cured conductive colloid includes solder paste, and the conductive film layer is a composite layer of a transparent conductive film layer and a metal conductive film layer.

[0026] Optionally, the metal conductive film layer includes at least one of copper, tin, gold, silver and nickel.

[0027] Optionally, the thickness of the metal conductive film layer is 20 nm-1000 nm.

[0028] Optionally, the metal conductive film layer is a metal stack arranged in sequence outward from the transparent conductive film layer, and the metal stack includes a first metal layer and a second metal layer, wherein the thickness of the first metal layer is 10nm-500nm, the thickness of the second metal layer is 10nm-500nm, and the second metal layer is at least one of tin, silver, nickel and copper.

[0029] In some optional embodiments of the present disclosure, the solder paste contains tin alloy particles and soldering flux, the content of the tin alloy particles is 90-99 wt %, and the content of the soldering flux is 1-10 wt %.

[0030] In some optional embodiments of the present disclosure, in the width direction of the back surface, a distance is left between the side edge of the cured conductive colloid and the edge of the adjacent isolation region.

[0031] In some optional embodiments of the present disclosure, the width of the cured conductive colloid is 10 μm-300 μm, optionally 10 μm-200 μm, and the thickness is 10 μm-100 μm.

[0032] In some optional embodiments of the present disclosure, the width of the conductive layer is 100μm-800μm, optionally 400μm-800μm, and the thickness of the conductive layer is 10μm-100μm, optionally 30μm-100μm; wherein the width of the conductive layer refers to the width of the portion of the conductive layer that is in contact with the corresponding conductive area.

[0033] In some optional embodiments of the present disclosure, the conductive layer includes a conductive metal layer, and an anti-oxidation coating is provided on the surface of the conductive metal layer or no anti-oxidation coating is provided.

[0034] Optionally, the material of the conductive metal layer includes at least one of copper foil, silver foil, gold foil, aluminum foil and tin foil.

[0035] In some optional embodiments of the present disclosure, the ratio of the width of the N-type conductive region to the width of the P-type conductive region is 2:3 to 1:1.

[0036] In some optional embodiments of the present disclosure, the width of the N-type conductive region is 200 μm-700 μm, the width of the P-type conductive region is 300 μm-800 μm, and the width of the isolation region is 30 μm-200 μm, optionally 50 μm-150 μm.

[0037] Optionally, the sum of the widths of adjacent N-type conductive regions, P-type conductive regions, and isolation regions is between 0.53 mm and 1.7 mm.

[0038] In some optional embodiments of the present disclosure, the busbar further includes a mask layer, which is disposed between adjacent cured conductive colloids and extends in width at least to an end edge of the isolation region.

[0039] Optionally, the thickness of the mask layer is ≥ (thickness of adjacent solidified conductive colloid×width of solidified conductive colloid / width of adjacent conductive layer on the contact surface with the corresponding conductive region).

[0040] In some optional embodiments of the present disclosure, the width of the mask layer is 100 μm-500 μm, and the thickness of the mask layer is 20 μm-100 μm, optionally 30 μm-100 μm.

[0041] In some optional embodiments of the present disclosure, the busbar further includes a carrier layer, and the conductive layer is disposed on the carrier layer in a desired pattern.

[0042] Optionally, one end of the mask layer away from the isolation region is embedded in the gap of the distribution pattern formed by the conductive layer and connected to the carrier layer.

[0043] In some optional embodiments of the present disclosure, several back-contact cells are arranged in sequence along the length direction of their N-type conductive regions and P-type conductive regions, and the length of the conductive layer extends along the length arrangement direction of the corresponding conductive regions of the several back-contact cells.

[0044] In some optional embodiments of the present disclosure, the N-type conductive region includes a first passivation layer and an N-type doped silicon layer, and the P-type conductive region includes a second passivation layer and a P-type doped silicon layer, and the first passivation layer and the second passivation layer are each independently selected from an intrinsic amorphous layer or a tunneling oxide layer.

[0045] In a second aspect, the present disclosure provides a method for manufacturing a back-contact cell string, wherein the back-contact cell string is the back-contact cell string described in the first aspect.

[0046] The first preparation method includes the following steps:

[0047] S1. Arrange several back-contact solar cells on a platform in sequence with their backs facing upwards;

[0048] S2. Coating a liquid gel-like conductive colloid or solder paste on a portion of the conductive film layer corresponding to the outer surface of the N-type conductive area and the P-type conductive area on the back side of the back contact solar cell;

[0049] S3, aligning and laminating the conductive layer contained in the busbar and the overall distribution pattern formed by the N-type conductive area and the P-type conductive area in the back contact battery sheet, applying pressure and performing preliminary curing;

[0050] S4, re-curing the battery string obtained after the initial curing.

[0051] In some optional embodiments of the present disclosure, when the conductive colloid is a UV-curable conductive colloid, the busbar is made of a material that can transmit ultraviolet light, and the initial curing is performed by irradiating a UV light source with an energy of 200 mJ / cm 2 -5000mJ / cm 2 .

[0052] The second production method includes the following steps:

[0053] S1. Lay the busbar with the conductive layer facing upward on the platform;

[0054] S2. Coating the exposed conductive layer surface of the busbar with liquid conductive colloid or solder paste;

[0055] S3. Place several back-contact solar cells with their backs facing downward, aligning and laminating the N-type conductive areas and P-type conductive areas thereof with the conductive layers on the busbars, applying pressure, and performing preliminary curing.

[0056] S4, re-curing the battery string obtained after the initial curing.

[0057] In some optional embodiments of the present disclosure, the platform has a vacuum adsorption structure, a heating mechanism and a cooling mechanism to respectively perform vacuum adsorption fixation, heating or cooling on objects placed on the platform. The heating mechanism and the cooling mechanism adjust the temperature of the platform to 30°C-150°C.

[0058] In some optional embodiments of the present disclosure, the method of coating the liquid colloidal conductive colloid or solder paste includes dispensing or inkjet printing, and the coating width is smaller than the width of the corresponding conductive area and not greater than the width of the exposed conductive layer on the corresponding busbar.

[0059] In some optional embodiments of the present disclosure, when the conductive colloid is introduced as a two-component colloid, the conditions for the preliminary curing include: a curing temperature of room temperature or 30° C.-50° C., and a curing time of 10 s-60 s.

[0060] In some optional embodiments of the present disclosure, when the conductive colloid is a single-component thermosetting conductive colloid or a UV-curable conductive colloid, the conditions for the preliminary curing include: a curing temperature of 50° C.-150° C. and a curing time of 15s-300s.

[0061] In some optional embodiments of the present disclosure, when applying the solder paste in S2, the conditions for the preliminary curing include: a curing temperature of 110°C-200°C.

[0062] In some optional embodiments of the present disclosure, the re-curing conditions include: a curing temperature of 50° C.-200° C., and a curing time of 0.1 h-2 h.

[0063] In a third aspect, the present disclosure provides a photovoltaic module comprising the back-contact cell string described in the first aspect. Beneficial effects:

[0064] The present disclosure adopts the above-mentioned technical solution, especially adopts a back-contact cell without metal electrodes and provided with an isolation area and a conductive film layer, in combination with a busbar provided with a conductive layer and a structure of a solidified conductive colloid, and the thickness of the conductive layer is suitable for the area and width of the P-type conductive area. In the case of adopting a back-contact cell without metal electrodes (i.e., without main and fine grid lines) and without a welding strip, it can effectively reduce the conductive power loss, which is conducive to balancing the conductive power loss with the material cost and reducing the electrode cost. Among them, the present disclosure adopts a solidified conductive colloid. On the one hand, it can improve the bonding strength between the conductive film layer and the conductive layer, fix the back-contact cell and the busbar, and maintain a good adhesion effect to ensure the reliability of the photovoltaic module (such as being able to pass the TC test (hot and cold cycle test), etc., which is very important for the reliability of each component of the photovoltaic module). On the second hand, the use of solidified conductive colloid for connection can greatly reduce the contact resistance between the metal contained in the conductive layer and the corresponding conductive film layer of the corresponding conductive area, forming a good conductive effect, which is conducive to improving the power of the battery string. Thirdly, by matching the thickness of the conductive layer with the area and width of the PN junction, the thickness of the conductive layer can be optimized to reduce the power loss of the conductive layer under different current densities, thereby ensuring a balance between conductive power loss and material cost.

[0065] Among them, the conductive areas of the back contact battery cell and the busbar are directly connected by solidifying the conductive colloid. The current is transmitted from the N-type conductive area or the P-type conductive area of ​​the back contact battery to the conductive layer of the busbar through the solidified conductive colloid. The transmission distance is in the range of 10μm-100μm (the optional transmission distance is only 30μm-50μm). Its transmission distance is less than one thousandth of the traditional metal electrode welding scheme, thereby reducing the current transmission link and reducing power loss. At the same time, the solidified conductive colloid can disperse the collected current. For example, in some embodiments, the current density is about one tenth of the traditional metal electrode welding scheme (collected and transmitted per square millimeter area), thereby improving the power of the battery string. In the conventional metal electrode welding scheme in the prior art, the current needs to be collected by the metal electrode and then converged to the busbar. It has a longer transmission distance of 10mm-20mm, a longer transmission distance, a higher current density, and higher loss.

[0066] Among them, the distribution pattern formed by the conductive layer disclosed in the present invention corresponds to the overall distribution pattern formed by the N-type conductive area and the P-type conductive area and is aligned. The conductive layer is extremely easy to pattern and can be arbitrarily processed according to the required shape of the back-contact battery (such as laser engraving pattern, etc.). At the same time, the conductive layer and other structures of the busbar (such as the carrier layer) can be integrally formed to ensure the accuracy of the electrode pattern, thereby helping to reduce the deviation between the conductive layer pattern and the N-type conductive area and the P-type conductive area, thereby reducing the short circuit or micro-short circuit defects caused by pattern mismatch, and improving the yield of the battery string or photovoltaic module; this is because for the back-contact battery with both positive and negative electrodes located on the back, alignment accuracy is particularly important.

[0067] Moreover, the isolation area provided in the back contact cell can effectively prevent the overflow of the solidified conductive colloid and cause a short circuit. The present disclosure is applicable to HBC back contact cells, TBC back contact solar cells based on tunneling polycrystalline structures, or back contact cells such as those with a combined passivation structure.

[0068] Under the same conditions, if a solidified conductive colloid and a conductive layer are not provided, but a metal wire (the metal contained in it is generally a copper wire in the industry) is provided on the busbar and the metal wire is directly connected to the conductive film layer, in this solution, there is no possibility of directly establishing a good connection between the two (this is because most metals and semiconductors cannot directly form an ohmic contact through bonding, and thus cannot obtain a good conductive effect). The two are only brought into contact through lamination when forming the assembly (that is, the two are only brought into contact through melting of the film after lamination). The two have no bonding strength, and the thermal expansion and contraction during reliability performance testing (such as TC testing (hot and cold cycle testing)) is sufficient to cause the two to lose contact, and lose their conductive function.

[0069] In the disclosed scheme of selecting a conductive layer and / or a cured conductive colloid with a suitable volume resistivity, both have a suitably low volume resistivity. The conductive layer, at a sufficient thickness, has a resistance comparable to that of a busbar, resulting in minimal power loss. Furthermore, the cured conductive colloid has a very short transmission distance (the cured conductive colloid has a thickness of 10 μm-100 μm), a relatively dispersed current, and a large conductive area, resulting in extremely low power loss.

[0070] In the solution disclosed herein, the conductive metal in the solidified conductive colloid may be a metal (the conductive metal is selected from at least one of silver, indium and tin) that can form an ohmic contact with the transparent conductive semiconductor in each conductive area. These metals can be configured to form an electrical connection between the metal and the semiconductor, and are easy to form a good ohmic contact with the corresponding conductive film layer of the corresponding conductive area, thereby reducing the contact resistance and further promoting the formation of a good conductive effect.

[0071] In the solution of the optional busbar disclosed in the present invention, a mask layer is further provided on the busbar. The main function of the mask layer is to limit the position of the solidified conductive colloid, thereby effectively avoiding the possibility of short circuit risk caused by overflow of the conductive colloid during the bonding process between the busbar and the back contact cell.

[0072] Since one busbar corresponds to multiple back-contact cells, and the overall distribution pattern formed by the N-type conductive area and the P-type conductive area needs to correspond to different areas of the busbar one by one, and the curing time is generally long (several minutes to tens of minutes), curing the back-contact cells one by one will take a long time in production. In this regard, in the manufacturing method of the back-contact cell string disclosed in the present invention, a two-step initial curing and re-curing is adopted, that is, a single back-contact cell is first initially cured to fix it on the busbar, and then the back-contact cell string is cured for a longer time to improve the bonding strength. This method is more suitable for the production of back-contact cell strings in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0074] Figure 1 is a top view of a back-contact battery string;

[0075] FIG2 is a cross-sectional view of the right side view of FIG1;

[0076] FIG3 is a partial bottom view of FIG1 .

[0077] FIG4 is a schematic diagram of the structure of a back contact cell without metal electrodes.

[0078] Explanation of the reference numerals 1. Back contact cell, 2n. N-type conductive region, 2p. P-type conductive region, 2g. Isolation region, 3. Cured conductive colloid, 4a. Carrier layer, 4b. Conductive layer, 4c. Mask layer. DETAILED DESCRIPTION

[0079] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Among them, the terms "optional" and "optional" all mean that they may be included or not (or may be present or not).

[0080] In a first aspect, the present disclosure provides a back-contact cell string comprising a plurality of back-contact cell sheets. The back-contact cell sheet comprises a silicon wafer, an N-type conductive region and a P-type conductive region disposed on the back side of the silicon wafer and alternately distributed along the width of the back side, and an isolation region located between the N-type conductive region and the P-type conductive region. The outer surfaces of the N-type conductive region and the P-type conductive region are each provided with a conductive film layer, the conductive film layer comprising a transparent conductive film layer or a composite layer comprising a transparent conductive film layer and a metal conductive film layer. The silicon wafer and the corresponding conductive region having a different conductivity type from the silicon wafer form a PN junction. The back-contact cell sheet does not contain a metal electrode, and the back-contact cell string further comprises a solidified conductive colloid and a busbar comprising a conductive layer. The busbar is attached to one side of the conductive film layer of the plurality of back-contact cell sheets via the conductive layer, and the distribution pattern formed by the conductive layer on the busbar corresponds to and is aligned with the overall distribution pattern formed by the N-type conductive region and the P-type conductive region. The solidified conductive colloid is disposed between the conductive layer and the conductive film layer.

[0081] The width of the conductive layer is 1 / 3 to 1 times, optionally 3 / 5 to 1 times, or optionally 4 / 5 to 1 times the width of the P-type conductive region, and the PN junction area is 20-40mm 2 The thickness of the conductive layer is 10-50μm, optionally 20-50μm; the PN junction area is 41-80mm 2 The thickness of the conductive layer is 51-100 μm. The thickness of the conductive layer disclosed herein is suitable for the area and width difference of the P-type conductive region. When combined with the cured conductive colloid, it can effectively reduce the conductive power loss and is more conducive to ensuring a balance between the conductive power loss and material cost.

[0082] The present disclosure connects a busbar and several back-contact battery cells together through the conductive layer of the busbar and the cured conductive glue.

[0083] The distribution pattern formed by the conductive layer on the busbar corresponds to the overall distribution pattern formed by the N-type conductive area and the P-type conductive area, and the arrangement is aligned. This means that each unit of the N-type conductive area and the P-type conductive area is provided with a conductive layer at a corresponding position in the thickness direction (the width of the corresponding conductive layer can be the same as or different from that of the corresponding conductive area), and the overall distribution pattern of the conductive layer on the busbar corresponds to the overall distribution pattern formed by the N-type conductive area and the P-type conductive area. Based on this, when preparing the conductive layer of the busbar, it can be etched into a corresponding conductive pattern based on the overall distribution pattern formed by the N-type conductive area and the P-type conductive area of ​​the back contact battery cell.

[0084] It can be understood in the present disclosure that the solidified conductive colloid is disposed on a portion of the conductive film layer corresponding to the outer surfaces of the N-type conductive region and the P-type conductive region.

[0085] In some optional embodiments of the present disclosure, the volume resistivity of the cured conductive colloid is not higher than 7×10-4 Ω·cm, optional not higher than 5×10 -4 Ω·cm, optional less than 1×10 -4 Ω·cm, or the volume resistivity of the conductive layer is not higher than 1×10 -4 Ω·cm, optional not higher than 1×10 -5 Ω·cm. Alternatively, the volume resistivity of the cured conductive colloid is not higher than 7×10 -4 Ω·cm, optional not higher than 5×10 -4 Ω·cm, optional less than 1×10 -4 Ω·cm, the volume resistivity of the conductive layer is not higher than 1×10 -4 Ω·cm, optional not higher than 1×10 -5 Ω·cm. Its suitable bulk resistivity can reduce current transmission loss and is more conducive to improving the conversion efficiency of back-contact battery strings or components.

[0086] In some optional embodiments of the present disclosure, the cured conductive colloid includes conductive glue or solder paste.

[0087] Optionally, the conductive adhesive comprises a gelatin matrix and a conductive component, wherein the conductive component includes a conductive metal and / or a conductive non-metal. The conductive component can be a single element (e.g., silver particles) or a multi-element composition; the multi-element composition can be a direct mixture or a coating structure of different elements (e.g., silver-coated copper particles).

[0088] Optionally, the content of the conductive component is 50-98 wt %.

[0089] Optionally, the content of the colloid matrix in the solidified conductive colloid is 2-50 wt %.

[0090] Optionally, the conductive non-metal includes at least one of graphite, graphene and carbon nanotubes.

[0091] Optionally, the conductive metal is selected from at least one of gold, silver, indium, copper, tin, aluminum, zinc, iron and nickel.

[0092] In some optional embodiments of the present disclosure, the cured conductive colloid includes conductive glue, and the conductive film layer is a transparent conductive film layer.

[0093] The type and thickness of the transparent conductive film layer disclosed herein are within conventional corresponding types and thickness ranges in the art, and can be, for example, at least one selected from tin-doped indium oxide (ITO), aluminum-doped zinc oxide, and tungsten-doped indium oxide. The thickness of the transparent conductive film layer can be, for example, 20-200 nm.

[0094] In some optional embodiments of the present disclosure, the conductive metal is a metal capable of forming an ohmic contact with the conductive film layer corresponding to each conductive region. Optionally, the conductive metal is at least one selected from silver, indium, and tin. In this optional solution, these metals can be configured to form an electrical connection between the metal and the semiconductor, and are easy to form a good ohmic contact with the corresponding conductive film layer of the corresponding conductive region, thereby reducing contact resistance and further promoting the formation of a good conductive effect.

[0095] In some optional embodiments of the present disclosure, the solidified conductive colloid further comprises a dispersing additive, and the content of the dispersing additive is 1-30 wt %, which is more conducive to improving the coating effect and bonding strength of the corresponding conductive colloid slurry.

[0096] Optionally, the dispersing additive includes at least one of alcohol, ketone and ester. Optionally, the dispersing additive includes at least one of acetone, methanol, ethanol, isopropanol and butyl acetate.

[0097] Optionally, the curable conductive colloid may further include other additives that improve the coating effect or bonding strength of the corresponding conductive colloid. For example, the additive may be at least one of a defoaming agent, a leveling agent, a flux (such as rosin), a diluent, and a curing agent. The additive content is preferably 0-10 wt%.

[0098] In some embodiments, the soldering flux may be rosin, which is a good soldering flux and can be in solution or powder form. For example, in tin soldering, applying a solution of rosin and alcohol to the soldered area can improve soldering performance. Alternatively, soldering with solder wire containing rosin powder can enhance soldering performance. In the present disclosure, mixing rosin powder or a rosin solution with tin alloy particles enhances soldering performance.

[0099] In some optional embodiments of the present disclosure, the conductive component exists in a granular form, which is more conducive to uniform distribution during the coating process to increase and reduce the volume resistivity of the cured conductive colloid, thereby achieving a balance between the bonding strength and conductivity of the cured conductive colloid.

[0100] The conductive adhesive disclosed herein may be an adhesive system adhesive. In some optional embodiments of the present disclosure, the adhesive matrix includes a resin.

[0101] Optionally, the resin includes at least one of epoxy resin, silicone resin, polyimide resin, phenolic resin, polyurethane and acrylic resin.

[0102] Optionally, the resin includes epoxy resin. The cured conductive colloid with epoxy resin as the colloid matrix can achieve low-temperature curing under the conditions of 30°C-150°C, and can be suitable for low-temperature connection of back-contact battery cells. Low-temperature connection can reduce the bending deformation of the back-contact battery cells, especially when using a flexible busbar, it can avoid conventional obvious deformation.

[0103] In some optional embodiments of the present disclosure, the solidified conductive colloid comprises solder paste, and the conductive film layer is a composite layer of a transparent conductive film layer and a metal conductive film layer. The addition of the metal conductive film layer facilitates fusion with the melted solder paste, improving solder paste adhesion and reducing contact resistance. Using a solder paste solution significantly improves peel strength, approaching or even exceeding 5N / mm. Properly increasing peel strength improves the reliability of back-contact cell strings fabricated using this method.

[0104] Optionally, the metal conductive film layer includes at least one of copper, tin, gold, silver, and nickel. The metal conductive film layer can be a single material layer or a stack of multiple material layers, such as a copper-tin metal stack, a nickel-copper metal stack, or a nickel-tin metal stack. It is understood that the first metal in the stack is disposed adjacent to the transparent conductive film layer. For example, in a copper-tin metal stack, copper is disposed adjacent to the transparent conductive film layer, and tin is disposed on the copper surface.

[0105] Optionally, the thickness of the metal conductive film layer is 20 nm-1000 nm.

[0106] Optionally, the metal conductive film layer is a metal stack arranged sequentially outwards close to the transparent conductive film layer, and the metal stack includes a first metal layer and a second metal layer.

[0107] Optionally, the thickness of the first metal layer is 10 nm-500 nm, and the thickness of the second metal layer is 10 nm-500 nm.

[0108] Optionally, the second metal layer is a metal or alloy that is easily soldered with tin, such as at least one of tin, silver, nickel, and copper.

[0109] In some optional embodiments of the present disclosure, the solder paste includes tin alloy particles and flux, wherein the content of the tin alloy particles is 90-99 wt %, and the content of the flux is 1-10 wt %. The solder paste can achieve bonding through melting of the tin.

[0110] In some optional embodiments of the present disclosure, a distance is left between the side edge of the solidified conductive colloid and the edge of the adjacent isolation area in the width direction of the back side, which is more conducive to preventing the solidified conductive colloid from overflowing and causing a short circuit in the isolation area.

[0111] In some optional embodiments of the present disclosure, the width of the cured conductive colloid is 10μm-300μm, optionally 10μm-200μm. The width is suitable and more conducive to providing sufficient attachment area, improving bonding strength, and effectively avoiding separation between the battery cell and the busbar to cause poor contact.

[0112] Optionally, the thickness of the solidified conductive colloid is 10 μm-100 μm, and the thickness is suitable for reducing the resistance of the solidified conductive colloid. Since the volume resistivity of the solidified conductive colloid is only 5×10 -5 Ω·cm, reducing the thickness of the cured conductive colloid is beneficial to reducing the current transmission distance, thereby reducing the resistance power loss of the cured conductive colloid.

[0113] In some optional embodiments of the present disclosure, when the silicon wafer is N-type, the area of ​​the P-type conductive region is 20-40 mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the P-type conductive region is 41-80mm 2 The thickness of the conductive layer is 51-100 μm.

[0114] In some optional embodiments of the present disclosure, when the silicon wafer is P-type, the area of ​​the N-type conductive region is 20-40 mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the N-type conductive area is 41-80mm 2 The thickness of the conductive layer is 51-100 μm.

[0115] In some optional embodiments of the present disclosure, the width of the conductive layer is 100 μm-800 μm, optionally 400 μm-800 μm, which is suitable for better matching with the corresponding conductive area. The width of the conductive layer refers to the width of the portion of the conductive layer that contacts the corresponding conductive area.

[0116] Optionally, the thickness of the conductive layer is 10 μm-100 μm, optionally 30 μm-100 μm. The thickness is appropriate, which is more conducive to adapting to the area of ​​the P-type conductive region, reducing current transmission loss, and saving material costs.

[0117] In some optional embodiments of the present disclosure, the conductive layer includes a conductive metal layer, and an anti-oxidation coating is provided on the surface of the conductive metal layer or not. It can be seen that the surface of the conductive metal layer can be provided with an anti-oxidation coating or not, and the choice can be made based on actual needs.

[0118] Optionally, an anti-oxidation coating is provided on the surface of the conductive metal layer, which is more conducive to avoiding the possibility of increased contact resistance due to easy oxidation during the corresponding conductive colloid coating process.

[0119] The specific material and thickness of the anti-oxidation coating can be any material as long as it can play an anti-oxidation role, for example, it can be at least one of a tin coating and a silver coating, etc. For example, the thickness of the anti-oxidation coating can be 2-30 μm.

[0120] Optionally, the material of the conductive metal layer includes at least one of copper foil, gold foil, silver foil, aluminum foil and tin foil.

[0121] In some optional embodiments of the present disclosure, the width ratio of the N-type conductive region to the P-type conductive region is 2:3 to 1:1. This width ratio is appropriate to minimize power loss and make the areas of the conductive layers corresponding to the N-type conductive region and the P-type conductive region closer.

[0122] In some optional embodiments of the present disclosure, the width of the N-type conductive region is 200 μm-700 μm, and the width of the P-type conductive region is 300 μm-800 μm, which is more conducive to improving battery efficiency.

[0123] Optionally, the sum of the widths of adjacent N-type conductive regions, P-type conductive regions and isolation regions is between 0.53 mm and 1.7 mm, which is more conducive to reducing the current size of the N-type conductive region and the P-type conductive region, thereby reducing the current transmission loss of the conductive layer.

[0124] Optionally, the width of the isolation region is 30 μm-200 μm, optionally 50 μm-150 μm.

[0125] In some optional embodiments of the present disclosure, the busbar further includes a mask layer, which is disposed between adjacent solidified conductive colloids and extends in width at least to the end edge of the isolation region, thereby further preventing the solidified conductive colloid from overflowing.

[0126] The mask layer is arranged between adjacent solidified conductive colloids and extends in width at least to the end edge of the isolation region, indicating that the width of the mask layer is ≥ the corresponding isolation region width, and optionally is greater than the corresponding isolation region width (i.e., the mask layer extends in the width direction to the end edge position across the isolation region and continues to extend).

[0127] Optionally, the thickness of the mask layer is ≥ (adjacent cured conductive colloid thickness × cured conductive colloid width / adjacent conductive layer width on the contact surface with the corresponding conductive area), which is more conducive to maximizing the overflow range of the cured conductive colloid and further avoiding the possibility of short circuit.

[0128] In some optional embodiments of the present disclosure, the width of the mask layer is 100 μm-500 μm, and the thickness of the mask layer is 20 μm-100 μm, optionally 30 μm-100 μm.

[0129] The mask layer disclosed in the present invention is made of an insulating film material, for example, it can be one or more of polyimide (PI), polyethylene (PE), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0130] In some optional embodiments of the present disclosure, the busbar further includes a carrier layer, and the conductive layer is disposed on the carrier layer in a desired pattern.

[0131] Optionally, one end of the mask layer, remote from the isolation region, is embedded in a gap in the distribution pattern formed by the conductive layer and optionally connected to the carrier layer. The mask layer may not extend to the surface of the conductive layer in the width direction, or may extend to a portion of the surface of the conductive layer (in which case, only a portion of the surface of the conductive layer is covered, with the remainder of the conductive layer exposed to connect to the portions of the conductive film layer corresponding to the outer surfaces of the N-type conductive region and the P-type conductive region via cured conductive colloid).

[0132] The material and thickness of the carrier layer described in the present disclosure can be selected from a wide range, as long as it can easily support the conductive layer. The primary material of the carrier layer can be an insulating film or plate material, which can be at least one of a flexible material such as PET film, PVC film, and PI film, or a rigid material such as at least one of fiberglass board, acrylic board, and glass. The thickness of the carrier layer can vary depending on the material and is not particularly limited in the present disclosure. The thickness of the carrier layer can, for example, range from 0.1 to 5 mm.

[0133] In some optional embodiments of the present disclosure, a plurality of back-contact solar cells are sequentially arranged along the length direction of their N-type conductive regions and P-type conductive regions, and the length of the conductive layer extends along the length arrangement direction of the corresponding conductive regions of the plurality of back-contact solar cells. In the present disclosure, the alignment method of the N-type conductive regions and P-type conductive regions of adjacent back-contact solar cells can be based on the method of the prior art and will not be further described here.

[0134] The thickness and material of the conductive film layer described in the present disclosure can be within the conventional range of the prior art, for example, the thickness can be 30 nm to 150 nm. For example, the material of the conductive film layer can be a doped indium oxide film layer (the doping element can be at least one of tin, tungsten, and zinc, such as tin-doped indium oxide ITO, tungsten-doped indium oxide IWO, or zinc-doped indium oxide IZO, etc.) or a doped tin oxide film layer (the doping element can be at least one of fluorine, antimony, aluminum, and zinc, such as fluorine-doped tin oxide FTO or aluminum-doped tin oxide ATO, etc.).

[0135] It is understood in the present disclosure that the N-type conductive region and the P-type conductive region each independently include a doped semiconductor layer corresponding to a corresponding conductive type, for example, the N-type conductive region includes a phosphorus-doped semiconductor layer.

[0136] In some optional embodiments of the present disclosure, the N-type conductive region includes a first passivation layer and an N-type doped silicon layer, and the P-type conductive region includes a second passivation layer and a P-type doped silicon layer, wherein the first passivation layer and the second passivation layer are each independently selected from an intrinsic amorphous layer or a tunneling oxide layer. The present disclosure is applicable to N-type conductive regions and P-type conductive regions of any passivation structure, as long as the N-type conductive regions and P-type conductive regions are alternately distributed and isolation regions are provided.

[0137] In a second aspect, the present disclosure provides a method for manufacturing a back-contact cell string, wherein the back-contact cell string is the back-contact cell string described in the first aspect.

[0138] The first preparation method includes the following steps:

[0139] S1. Arrange several back-contact solar cells on a platform in sequence with their backs facing upwards;

[0140] S2. Coating a liquid gel-like conductive colloid or solder paste on a portion of the conductive film layer corresponding to the outer surface of the N-type conductive area and the P-type conductive area on the back side of the back contact solar cell;

[0141] S3, aligning and laminating the conductive layer contained in the busbar and the overall distribution pattern formed by the N-type conductive area and the P-type conductive area in the back contact battery sheet, applying pressure and performing preliminary curing;

[0142] S4, re-curing the battery string obtained after the initial curing.

[0143] In some optional embodiments of the present disclosure, when the conductive colloid is a UV-curable conductive colloid, the busbar is made of a material that can transmit ultraviolet light, and the initial curing is performed by irradiating a UV light source with an energy of 200 mJ / cm 2 -5000mJ / cm 2 The initial curing has no special requirements on temperature.

[0144] It is understood that the UV-curable conductive colloid described in this disclosure also includes a photoinitiator, which is configured to open the chemical bonds of the photosensitive groups in the side chains of the polymer matrix molecules under UV light, and then recombine with the opened chemical bonds of adjacent molecules, thereby cross-linking and curing. Generally speaking, photoinitiators can be divided into two types: aryl alkyl ketone compounds (cleavage-type free radical photoinitiators) and dibenzophenone or heterocyclic aromatic ketone compounds (hydrogen abstraction-type free radical photoinitiators), both of which can be used in this disclosure; this is prior art and will not be repeated here.

[0145] The second production method includes the following steps:

[0146] S1. Lay the busbar with the conductive layer facing upward on the platform;

[0147] S2. Coating the exposed conductive layer surface of the busbar with liquid conductive colloid or solder paste;

[0148] S3. Place several back-contact solar cells with their backs facing downward, aligning and laminating the N-type conductive areas and P-type conductive areas thereof with the conductive layers on the busbars, applying pressure, and performing preliminary curing.

[0149] S4, re-curing the battery string obtained after the initial curing.

[0150] The busbar described in this disclosure is prepared in advance. The method of preparation is not limited in this disclosure, as long as the desired layer structure can be formed. The overall distribution pattern of the conductive layer contained in the busbar can be formed in accordance with the overall pattern formed by the N-type conductive region and the P-type conductive region on the back contact solar cell. The conductive layer can be formed, for example, using a masked etching method (similar to the production of PCB boards).

[0151] Optionally, when the busbar further includes a mask layer, the preparation process may be to prepare the mask layer after the conductive layer is formed. The method for preparing the mask layer may be, for example, laminating the entire surface with a film and then patterning and etching with a laser.

[0152] In some optional embodiments of the present disclosure, the platform includes a vacuum adsorption structure, a heating mechanism, and a cooling mechanism to respectively vacuum adsorb and fix, heat, or cool an object placed on the platform. The present disclosure does not limit the specific structures of the vacuum adsorption structure, heating mechanism, and cooling mechanism, as long as they can achieve the corresponding desired functions.

[0153] Optionally, the heating mechanism and the cooling mechanism can adjust the temperature of the platform to 30° C.-150° C. The temperature control in subsequent processes can be regulated by the platform.

[0154] In some optional embodiments of the present disclosure, the liquid gel-like conductive colloid or solder paste is applied by dispensing or inkjet printing, with the coating width being smaller than the width of the corresponding conductive area and no larger than the width of the exposed conductive layer on the corresponding busbar. The liquid gel-like conductive colloid is subsequently re-cured to form a solidified conductive colloid.

[0155] In some optional embodiments of the present disclosure, when the conductive colloid is introduced as a two-component colloid, the initial curing conditions include: a curing temperature of room temperature or 30°C-50°C, and a curing time of 10s-60s. A two-component colloid refers to a colloid comprising a glue A (e.g., a main agent containing conductive component particles and a colloid matrix, such as a polymer matrix) and a glue B (e.g., a curing agent). Both are fluids before mixing. When applied by dispensing, the two are squeezed out of their respective tubes, mixed together, and then applied to the workpiece. The mixed colloid quickly solidifies at room temperature without the need for heating.

[0156] In some optional embodiments of the present disclosure, when the conductive colloid is introduced as a single-component thermosetting conductive colloid or a UV-curable conductive colloid, the initial curing conditions include: a curing temperature of 50°C to 150°C and a curing time of 15s to 300s. The single-component conductive colloid is packaged in a single unit and introduced directly, requiring heating for curing.

[0157] In the above optional scheme of the present disclosure, matching different initial curing temperatures for conductive colloids of different compositions can reduce the bending deformation of the back contact battery cells during the production of the back contact battery string, and is more conducive to further avoiding the risk of defects such as short circuit of the back contact battery string caused by deformation dislocation.

[0158] In some optional embodiments of the present disclosure, when applying the solder paste in S2, the initial curing conditions include: a curing temperature of 110°C to 200°C, optionally 120°C to 145°C. Using this optional curing temperature increases the bonding strength and peel strength of the solder paste, while effectively avoiding excessive stress during solder paste formation, which may lead to local defects caused by stress release.

[0159] Optionally, when applying the solder paste in S2, the time for the initial curing can be selected according to the curing conditions, for example, it can be 10-60 seconds.

[0160] In some optional embodiments of the present disclosure, the re-curing conditions include: a curing temperature of 50° C.-200° C., and a curing time of 0.1 h-2 h.

[0161] The pressurization pressure disclosed in the present invention can be selected in a wide range, as long as it is conducive to the initial combination of the back contact battery cell and the busbar without any gaps, and can be optionally controlled within 5-30N.

[0162] In the manufacturing method disclosed herein, the N-type conductive region of a back-contact cell and the P-type conductive region of an adjacent back-contact cell are connected in series to form a back-contact cell string.

[0163] In a third aspect, the present disclosure provides a photovoltaic module comprising the back-contact cell string described in the first aspect.

[0164] Conventional components such as backsheets, adhesive films, and front sheets may or may not be provided in the photovoltaic modules of the present disclosure according to actual needs. For example, whether a backsheet is provided can be selected based on the strength or flexibility requirements of the photovoltaic modules. This is because some of the carrier layers of the busbars of the present disclosure can be directly used as backsheets, such as glass and fiberglass boards. If the carrier layer is a flexible film material, such as at least one of PET film, PVC film, and PI film, a semi-flexible module can be formed. However, if higher mechanical strength is required, adding a backsheet (such as a glass backsheet, TPT solar backsheet, TPE solar backsheet, BBF solar backsheet, APE solar backsheet, or EVA solar backsheet) to the back is also a feasible approach, and the back-contact cell string structure of the present disclosure can be applied.

[0165] In the preparation of photovoltaic modules, if the conventional modules need to be laminated, the lamination can be achieved in the re-curing step, that is, the conventional modules of the photovoltaic module are directly stacked on top in the manufacturing method of the back contact cell string, and the lamination is achieved by subsequent re-curing.

[0166] The embodiments of the present disclosure are described in detail below, which are exemplary and only used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0167] Example 1

[0168] A back-contact battery string, the structure of which is shown in FIG1 , FIG2 and FIG3 , includes a plurality of back-contact battery cells 1 , a busbar and a solidified conductive colloid 3 .

[0169] Specifically, there are 10 back-contact cells 1. The structure of the back-contact cell 1 is shown in Figure 4. It includes an N-type silicon wafer, an N-type conductive region 2n and a P-type conductive region 2p arranged on the back of the N-type silicon wafer and alternately distributed along the width of the back, and an isolation region 2g located between the N-type conductive region 2n and the P-type conductive region 2p. The outer surfaces of the N-type conductive region 2n and the P-type conductive region 2p are respectively provided with a transparent conductive film layer and no metal electrode. The area of ​​the P-type conductive region 2p is 39.5mm 2 , width is 500μm, and the area of ​​N-type conductive region 2n is 31.6mm 2 , the width is 400μm, and the width of the isolation region 2g is 100μm.

[0170] The busbar is composed of a carrier layer 4a (specifically a PET film with a thickness of 0.5 mm), a conductive layer 4b (its main body is copper foil, and a tin plating layer with a thickness of 5 μm is provided on the outside of the copper foil) and a mask layer 4c (specifically a PI material). As shown in Figures 1, 2 and 3, the length of the conductive layer 4b extends along the length arrangement direction of the corresponding conductive areas of several back-contact battery cells 1; the busbar is attached to one side of the transparent conductive film layer of all back-contact battery cells 1 through the conductive layer 4b, and the distribution pattern formed by the conductive layer 4b on the busbar corresponds to and is aligned with the overall distribution pattern formed by the N-type conductive area 2n and the P-type conductive area 2p; the mask layer 4c is arranged between adjacent solidified conductive colloids 3 and extends in width and spans the end edge of the isolation area 2g. The end of the mask layer 4c away from the isolation area 2g is embedded in the gap of the distribution pattern formed by the conductive layer 4b and is connected to the carrier layer 4a. The width of the conductive layer 4b is 400 μm, the thickness of the conductive layer 4b is 40 μm, and the volume resistivity is 2×10 -6 Ω·cm; wherein the width of the conductive layer 4b refers to the width of the portion of the conductive layer 4b that contacts the corresponding conductive region. The width of the mask layer 4c is 200 μm, and the thickness of the mask layer 4c is 40 μm.

[0171] The solidified conductive colloid 3 is disposed between the conductive layer 4b and the transparent conductive film layer to connect the busbar and the back contact cell 1. The solidified conductive colloid 3 has a width of 200 μm, a thickness of 50 μm, and a volume resistivity of 5×10 -5 Ω·cm. The cured conductive colloid 3 (specifically, conductive silver paste) is composed of epoxy resin, conductive silver particles, a dispersing additive, and an auxiliary agent. The content of the conductive silver particles is 85wt%, the content of the epoxy resin is 13wt%, the content of the dispersing additive (specifically, butyl acetate) is 1wt%, and the content of the auxiliary agent (specifically, a curing agent) is 1wt%.

[0172] The back contact battery string is obtained by the following manufacturing method:

[0173] S1. Arrange several back-contact solar cells 1 on a platform in sequence along the length direction of their N-type conductive regions 2n and P-type conductive regions 2p with their backs facing upward, as shown in FIG1 and FIG3 ;

[0174] S2. Applying a liquid gel-like conductive colloid on the portion of the transparent conductive film layer corresponding to the outer surface of the N-type conductive region 2n and the P-type conductive region 2p on the back side of the back contact cell 1; the coating method is dispensing, and the coating width and thickness are determined according to the width and thickness of the solidified conductive colloid 3 to be formed;

[0175] S3. Align and bond the conductive layer 4b contained in the busbar with the overall distribution pattern formed by the N-type conductive region 2n and the P-type conductive region 2p in the back contact cell 1, apply pressure to 20N, and perform preliminary curing at 50°C for 30s.

[0176] S4. The battery string obtained after the initial curing is further cured at 150° C. for 1800 s.

[0177] Example 2

[0178] The method of Example 1 was followed, except that the composition of the cured conductive colloid was adjusted so that the volume resistivity was 5×10 -4 Ω·cm, specifically, the content of silver particles in the composition of the cured conductive colloid is adjusted to 75wt%, the contents of other dispersing additives and auxiliary agents remain unchanged, and the epoxy resin makes up 100% of the total amount.

[0179] Example 3

[0180] The method of Example 1 was followed, except that the conductive silver particles in the composition of the solidified conductive colloid were replaced with silver-coated copper particles (i.e., a structure with copper as the core and silver as the surface coating. The copper in the particle state is very easy to oxidize, and the silver coating maintains the conductive stability). The amount of silver particles used remained unchanged. In this case, the volume resistivity of the solidified conductive colloid was 1×10 -4 Ω·cm.

[0181] Example 4

[0182] The method of Example 1 was followed, except that the conductive silver particles in the composition of the solidified conductive colloid were replaced with conductive graphite particles, and the amount thereof remained unchanged. In this case, the volume resistivity of the solidified conductive colloid was 7×10 -4 Ω·cm.

[0183] Example 5

[0184] The method of Example 1 was used, except that the width of the cured conductive colloid was 300 μm.

[0185] Example 6

[0186] The method of Example 1 is referred to, except that the width of the conductive layer is adjusted to 300 μm, so that the width thereof is 60% of the width of the P-type conductive region.

[0187] Example 7

[0188] The method of Example 1 was followed, except that the thickness of the conductive layer was adjusted to 10 μm.

[0189] Example 8

[0190] The method of Example 1 is followed, except that the area of ​​the P-type conductive region is 80 mm 2 , the thickness of the conductive layer is 55μm.

[0191] Example 9

[0192] The method of Example 1 is referred to, except that the thickness of the mask layer is adjusted to 20 μm.

[0193] Example 10

[0194] The method of embodiment 1 is referred to, except that the width of the mask layer is adjusted to be the same as the width of the isolation region.

[0195] Example 11

[0196] The method of Example 1 is referred to, except that no mask layer is provided on the busbar.

[0197] Example 12

[0198] The method of Example 1 is referred to, except that the preparation method is different. The specific steps are as follows:

[0199] S1. Lay the busbar with the conductive layer facing upward on the platform;

[0200] S2. The exposed conductive layer surface of the busbar is coated with a liquid gel-like conductive colloid;

[0201] S3. Place several back-contact solar cells with their backs facing downward, aligning and laminating the N-type conductive areas and P-type conductive areas thereof with the conductive layers on the busbars, applying pressure, and performing preliminary curing.

[0202] S4, re-curing the battery string obtained after the initial curing, wherein the process parameters remain the same.

[0203] Example 13

[0204] The method of Example 1 was followed, except that a copper-tin metal laminate with a thickness of 20 nm and a thickness of 30 nm was applied to the outer surface of the transparent conductive film layer in the back-contact cell. In S2, tin paste (instead of conductive colloid) was applied as the connecting material between the back-contact cell and the busbar. The initial curing conditions in S3 were: constant pressure, a curing temperature of 135°C, and a curing time of 20 seconds.

[0205] Example 14

[0206] The method of Example 13 was used, except that the curing temperature in the preliminary curing was 110°C.

[0207] Example 15

[0208] The method of Example 13 was used, except that the curing temperature in the preliminary curing was 150°C.

[0209] Comparative Example 1

[0210] The method of Example 1 is referred to, except that a conventional back-contact cell with a metal electrode structure and a conventional busbar are used; wherein, compared with the back-contact cell of Example 1, the back-contact cell used further includes metal electrodes provided on the corresponding outer surfaces of the N-type conductive region and the P-type conductive region; and compared with the busbar of Example 1, the structure of the busbar used is not coated with a liquid gel-like conductive colloid, that is, no solidified conductive colloid is formed.

[0211] Comparative Example 2

[0212] The method of Example 1 is referred to, except that the structure of the busbar is different, specifically, the liquid gel-like conductive colloid is not coated, that is, no solidified conductive colloid is formed.

[0213] Comparative Example 3

[0214] The method of Example 1 was referred to, except that the thickness of the conductive layer was adjusted to 5 μm.

[0215] Comparative Example 4

[0216] The method of Example 1 is followed, except that the area of ​​the P-type conductive region is 80 mm 2 .

[0217] Comparative Example 5

[0218] The method of Example 1 is referred to, except that the width of the conductive layer is adjusted to 100 μm, so that the width thereof is 20% of the width of the P-type conductive region.

[0219] Test Case

[0220] The back-contact cell strings obtained in the above examples and comparative examples (hereinafter referred to as cell strings) were subjected to various performance tests using the same methods, with the results shown in Table 1. The peel strength test was conducted in accordance with the test standard: GB / T2791-1995; the series resistance Rs test, the parallel resistance Rsh test, and the cell string power W (6 G1 cells) test were all conducted in accordance with the test standard: GB / T6495.1-1996 Photovoltaic Devices Part 1: Measurement of Photovoltaic Current-Voltage Characteristics; and the cell string power attenuation test after TC50 was conducted in accordance with IEC61730-2.

[0221] Table 1

[0222] The above results show that, compared with the comparative example, the embodiment of the present disclosure can reduce the series resistance of the battery string and increase the parallel resistance, which is conducive to improving the battery string power. However, the comparative example has a relatively large series resistance and low power.

[0223] Optionally, according to Examples 1 and 2-12, it can be seen that the use of the optional back-contact battery string structure disclosed in the present invention can further reduce the series resistance of the battery string or component, which is more conducive to the improvement of the power of the battery string or component. Among them, according to the comparison between Example 1 and Examples 5, 9, and 11, the use of the optional key layer and its size scheme has a larger parallel resistance, which can effectively avoid the hidden danger of leakage while taking into account the improvement of the battery string power. According to the comparison between Example 13 and Example 14 and Example 15, it can be seen that the use of the optional metal conductive film layer, solder paste and its curing temperature scheme can greatly improve the peel strength, reduce the series resistance of the battery string, increase the parallel resistance, further help to improve the battery string power, and reduce the battery string power attenuation.

[0224] The above describes in detail the optional embodiments of the present disclosure, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure can be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present disclosure and fall within the scope of protection of the present disclosure. Industrial Applicability

[0225] The present disclosure provides a back-contact cell string, a method for manufacturing the same, and a photovoltaic module. The back-contact cell string can realize the use of back-contact cell sheets without metal electrodes (i.e., without main grid lines), thereby reducing electrode costs, reducing current transmission links, and reducing power losses. At the same time, the solidified conductive colloid can disperse the collected current and improve the power of the cell string.

Claims

1. A back-contact cell string, comprising a plurality of back-contact cell cells, the back-contact cell cells comprising a silicon wafer, an N-type conductive region and a P-type conductive region disposed on the back side of the silicon wafer and alternately distributed along the width direction of the back side, and an isolation region located between the N-type conductive region and the P-type conductive region, the outer surfaces of the N-type conductive region and the P-type conductive region respectively being provided with a conductive film layer, the conductive film layer comprising a transparent conductive film layer or a composite layer comprising a transparent conductive film layer and a metal conductive film layer, the silicon wafer and the corresponding conductive region having a different conductivity type from the silicon wafer forming a PN junction, characterized in that: There is no metal electrode in the back contact battery cell, and the back contact battery string also includes a solidified conductive colloid and a busbar containing a conductive layer, the busbar is attached to one side of the conductive film layer of the plurality of back contact battery cells through the conductive layer, and the distribution pattern formed by the conductive layer on the busbar corresponds to the overall distribution pattern formed by the N-type conductive area and the P-type conductive area and is arranged in alignment, the solidified conductive colloid is arranged between the conductive layer and the conductive film layer, the width of the conductive layer is 1 / 3 to 1 times the width of the P-type conductive area; and the PN junction area is 20-40mm 2 The thickness of the conductive layer is 10-50μm, and the PN junction area is 41-80mm 2 The thickness of the conductive layer is 51-100 μm.

2. The back contact cell string according to claim 1, characterized in that The volume resistivity of the cured conductive colloid is not higher than 7×10 -4 Ω·cm, and / or the volume resistivity of the conductive layer is not higher than 1×10 -4 Ω·cm.

3. The back contact cell string according to claim 1 or 2, characterized in that: The solidified conductive colloid includes conductive glue or solder paste; When the solidified conductive colloid comprises a conductive adhesive, the conductive film layer is a transparent conductive film layer; the conductive adhesive comprises a colloid matrix and a conductive component, the conductive component comprises a conductive metal and / or a conductive non-metal, the content of the conductive component is 50-98wt%, the conductive non-metal comprises at least one of graphite, graphene and carbon nanotubes, and the conductive metal is selected from at least one of gold, silver, indium, copper, tin, aluminum, zinc, iron and nickel; When the solidified conductive colloid includes solder paste, the conductive film layer is a composite layer of a transparent conductive film layer and a metal conductive film layer, the metal conductive film layer includes at least one of copper, tin, gold, silver and nickel, and the thickness of the metal conductive film layer is 20nm-1000nm; the solder paste contains tin alloy particles and flux, the content of the tin alloy particles is 90-99wt%, and the content of the flux is 1-10wt%.

4. The back contact cell string according to claim 3, characterized in that: The metal conductive film layer is a metal stack arranged in sequence outward from the transparent conductive film layer, and the metal stack includes a first metal layer and a second metal layer, wherein the thickness of the first metal layer is 10nm-500nm, the thickness of the second metal layer is 10nm-500nm, and the second metal layer is at least one of tin, silver, nickel and copper.

5. The back contact cell string according to claim 3 or 4, characterized in that: The conductive adhesive further has at least one of the following structures: Structure 1: The solidified conductive colloid includes a conductive metal, wherein the conductive metal is a metal capable of forming an ohmic contact with the conductive film layer corresponding to each conductive region, and the conductive metal is selected from at least one of silver, indium, and tin; Structure 2: The colloid matrix includes a resin, and the resin includes at least one of epoxy resin, silicone resin, polyimide resin, phenolic resin, polyurethane and acrylic resin; Structure 3: The conductive adhesive further includes a dispersing additive and an auxiliary agent, wherein the content of the dispersing additive is 1-30 wt %. The content of the auxiliary agent is 0-10wt%, the dispersing additive includes at least one of acetone, methanol, ethanol, isopropyl alcohol and butyl acetate, and the auxiliary agent includes at least one of a defoaming agent, a leveling agent, a flux, a diluent and a curing agent; Structure 4: The conductive component exists in a granular form.

6. The back contact cell string according to any one of claims 1 to 5, characterized in that In the width direction of the back surface, a distance is left between the side edge of the solidified conductive colloid and the edge of the adjacent isolation area; and / or, The cured conductive colloid has a width of 10 μm-300 μm and a thickness of 10 μm-100 μm.

7. The back contact cell string according to any one of claims 1 to 6, characterized in that When the silicon wafer is N-type, the area of ​​the P-type conductive region is 20-40mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the P-type conductive region is 41-80mm 2 The thickness of the conductive layer is 51-100μm; in the case of P-type silicon wafer, the area of ​​the N-type conductive area is 20-40mm 2 The thickness of the conductive layer is 10-50μm, and the area of ​​the N-type conductive area is 41-80mm 2 When the thickness of the conductive layer is 51-100 μm; And / or, the conductive layer has at least one of the following structures: Structure 1: The width of the conductive layer is 100 μm-800 μm, and the thickness of the conductive layer is 10 μm-100 μm; wherein the width of the conductive layer refers to the width of the portion of the conductive layer that contacts the corresponding conductive area; Structure 2: The conductive layer includes a conductive metal layer, and an anti-oxidation coating is provided on the surface of the conductive metal layer or no anti-oxidation coating is provided; wherein the material of the conductive metal layer includes at least one of copper foil, silver foil, gold foil, aluminum foil and tin foil.

8. The back contact cell string according to any one of claims 1 to 7, characterized in that The width ratio of the N-type conductive region to the P-type conductive region is 2:3 to 1:1; and / or, The width of the N-type conductive region is 200 μm-700 μm, the width of the P-type conductive region is 300 μm-800 μm, and the width of the isolation region is 30 μm-200 μm; the sum of the widths of adjacent N-type conductive regions, P-type conductive regions and isolation regions is between 0.53 mm and 1.7 mm.

9. The back contact cell string according to any one of claims 1 to 8, characterized in that The busbar further includes a mask layer, which is disposed between adjacent cured conductive colloids and extends in width at least to the end edge of the isolation region.

10. The back contact cell string according to claim 9, characterized in that: The thickness of the mask layer is ≥ the thickness of the adjacent solidified conductive colloid × the width of the solidified conductive colloid / the width of the adjacent conductive layer on the contact surface with the corresponding conductive area; and / or, The width of the mask layer is 100 μm-500 μm, and the thickness of the mask layer is 20 μm-100 μm.

11. The back contact cell string according to claim 9 or 10, characterized in that: The busbar further comprises a carrier layer, the conductive layer is arranged on the carrier layer in a desired pattern, and one end of the mask layer away from the isolation region is embedded in the gap of the distribution pattern formed by the conductive layer and connected to the carrier layer.

12. The back contact cell string according to any one of claims 9 to 11, characterized in that A plurality of back-contact cells are sequentially arranged along the length direction of their N-type conductive regions and P-type conductive regions, and the length of the conductive layer extends along the length arrangement direction of the corresponding conductive regions of the plurality of back-contact cells; and / or, The N-type conductive region includes a first passivation layer and an N-type doped silicon layer, and the P-type conductive region includes a second passivation layer and a P-type doped silicon layer. The first passivation layer and the second passivation layer are independently selected from an intrinsic amorphous layer or a tunneling oxide layer.

13. A method for manufacturing a back contact battery string, characterized in that: The back-contact cell string is a back-contact cell string according to any one of claims 1 to 12, and a manufacturing method thereof comprises the following steps: S1. Arrange several back-contact solar cells on a platform in sequence with their backs facing upwards; S2. Coating a liquid gel-like conductive colloid or solder paste on a portion of the conductive film layer corresponding to the outer surface of the N-type conductive area and the P-type conductive area on the back side of the back contact solar cell; S3, aligning and laminating the conductive layer contained in the busbar and the overall distribution pattern formed by the N-type conductive area and the P-type conductive area in the back contact battery sheet, applying pressure and performing preliminary curing; S4, re-curing the battery string obtained after the initial curing.

14. The method for manufacturing a back contact battery string according to claim 13, wherein: When the conductive colloid is a UV curable conductive colloid, the busbar is made of a material that can transmit ultraviolet light, and the initial curing is performed by irradiating a UV light source, and the energy of the UV curing is 200mJ / cm 2 -5000mJ / cm 2 .

15. A method for manufacturing a back contact battery string, characterized in that: The back-contact cell string is a back-contact cell string according to any one of claims 1 to 12, and a manufacturing method thereof comprises the following steps: S1. Lay the busbar with the conductive layer facing upward on the platform; S2. Coating the exposed conductive layer surface of the busbar with liquid conductive colloid or solder paste; S3. Place several back-contact solar cells with their backs facing downward, aligning and laminating the N-type conductive areas and P-type conductive areas thereof with the conductive layers on the busbars, applying pressure, and performing preliminary curing. S4, re-curing the battery string obtained after the initial curing.

16. The method for manufacturing a back contact battery string according to any one of claims 13 to 15, characterized in that: The platform has a vacuum adsorption structure, a heating mechanism and a cooling mechanism to respectively perform vacuum adsorption fixation, heating or cooling on the objects placed on the platform. The heating mechanism and the cooling mechanism enable the platform to be adjusted to a temperature between 30°C and 150°C. and / or, The method of coating the liquid gel-like conductive colloid or solder paste includes dispensing or inkjet printing, and the coating width is smaller than the width of the corresponding conductive area and not larger than the width of the exposed conductive layer on the corresponding busbar.

17. The method for manufacturing a back contact battery string according to claim 13 or claim 15, characterized in that: When a liquid colloid conductive colloid is applied in S2, and when the conductive colloid is introduced as a two-component colloid, the conditions for the preliminary curing include: a curing temperature of room temperature or 30°C-50°C, and a curing time of 10s-60s; and when the conductive colloid is introduced as a single-component thermosetting conductive colloid or a UV-curing conductive colloid, the conditions for the preliminary curing include: a curing temperature of 50°C-150°C, and a curing time of 15s-300s; when solder paste is applied in S2, the conditions for the preliminary curing include: a curing temperature of 110°C-200°C; and / or, The re-curing conditions include: a curing temperature of 50° C.-200° C., and a curing time of 0.1 h-2 h.

18. A photovoltaic module, characterized in that: It comprises a back-contact cell string as claimed in any one of claims 1 to 12.

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