TBC solar cell back contact electrode, preparation method thereof and TBC solar cell

Abstract

The invention provides a TBC solar cell back contact electrode, a preparation method thereof and a TBC solar cell, and the preparation method comprises the steps: synchronously completing the laser grooving of an anti-reflection layer and the chemical deposition of a seed layer through laser chemical deposition, and preparing a metallized electrode on the surface of the obtained seed layer to obtain the TBC solar cell back contact electrode. Laser adopted in the laser chemical metal deposition is nanosecond pulse laser. According to the preparation method provided by the invention, the etching of the anti-reflection layer and the in-situ deposition of the seed layer are synchronously completed through laser chemical metal deposition and nanosecond pulse laser, so that the graphical preparation of the grid line region is realized in one step; according to the preparation method, the equipment investment is remarkably reduced, the material utilization rate is improved, pattern alignment can be well achieved, the integrity of the passivation layer is controlled and protected by means of instantaneous energy of laser, and a low-cost, high-precision and low-damage back contact electrode preparation scheme is provided for the TBC solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and relates to a method for preparing a back contact electrode of a TBC solar cell, and more particularly to a back contact electrode of a TBC solar cell, its preparation method, and a TBC solar cell. Background Technology

[0002] Traditional TBC batteries generally use screen-printed silver paste, which faces problems such as high electrode series resistance, high cost due to expensive silver paste, and recombination loss caused by metal diffusion.

[0003] In comparison, copper electroplating offers significant advantages: First, it allows for a better electrode aspect ratio, improving current collection efficiency; second, copper electrodes obtained through electroplating exhibit lower ohmic losses, enhancing battery performance; third, it reduces shading losses and increases light absorption utilization; fourth, it significantly improves battery conversion efficiency; and fifth, it completely avoids the use of expensive silver paste, drastically reducing production costs. These advantages make copper electroplating an ideal solution for overcoming the current bottlenecks in TBC battery metallization technology.

[0004] However, in traditional copper electroplating processes, a PVD seed layer needs to be deposited first, followed by copper electroplating on the surface of the seed layer. This traditional copper electroplating process has several drawbacks. The PVD seed layer needs to be deposited over the entire surface, resulting in low material utilization and thus high costs. Furthermore, insufficient alignment accuracy affects the reliability of electrode contact.

[0005] To improve the shortcomings of traditional copper electroplating processes, existing technologies employ a three-step process: laser patterning, deposition of a PVD seed layer, and copper electroplating. However, this three-step process has several problems: firstly, PVD equipment is expensive and requires deposition on the entire surface, resulting in low material utilization and increased costs; secondly, the cumulative alignment error caused by multiple processes affects the electrode contact accuracy.

[0006] CN120076456A discloses a method for electrode metallization of a back contact battery, belonging to the field of solar cell technology. The method involves printing dotted silver paste on the back of the back contact battery and drying and sintering it; printing solder paste on top of the silver paste and drying it; printing adhesive between the two solder pastes; laying the back contact battery with the printed solder paste and adhesive on a metal foil, ensuring close adhesion between the metal foil and the back contact battery; heating to melt and then solidify the solder paste to achieve welding between the back contact battery and the metal foil; simultaneously, curing the adhesive; and cutting the metal foil to complete the electrode metallization of the back contact battery, thus obtaining a back contact battery string.

[0007] CN118156333A discloses a low-cost metal electrode back-contact battery, its fabrication method, and a battery module. The battery includes a silicon wafer, a semiconductor distribution layer and a conductive film layer disposed on the back of the silicon wafer. The semiconductor distribution layer includes a first semiconductor layer and a second semiconductor layer, with a second semiconductor opening region formed between adjacent first semiconductor layers. It also includes a metal conductive film layer and a solderable conductive film layer sequentially disposed on the outer surface of the conductive film layer, as well as a first insulating ink and a second insulating ink. An isolation groove is formed on the conductive film layer corresponding to the edge region of the second semiconductor opening region, extending outwards through the metal conductive film layer and the solderable conductive film layer within the corresponding region. This invention significantly reduces the thickness and amount of insulating ink, significantly reduces the height of the grid lines, eliminates the need for silver paste fine grids and main grids, significantly reduces battery costs, and maintains excellent battery performance.

[0008] In summary, the existing methods for fabricating back contact electrodes for TBC solar cells all have certain drawbacks. These include high equipment costs and low material utilization, leading to higher overall costs. Furthermore, the cumulative pattern alignment is poor due to the multiple processing steps, resulting in insufficient electrode contact precision. Therefore, developing a novel back contact electrode for TBC solar cells and its fabrication method is crucial for the development of TBC solar cells. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a back contact electrode for TBC solar cells, its fabrication method, and the TBC solar cell itself. The fabrication method provided by the present invention utilizes laser chemical metal deposition and nanosecond pulsed lasers to simultaneously complete the etching of the anti-reflection layer and the in-situ deposition of the seed layer, achieving patterned fabrication of the grid area in one step. This fabrication method not only significantly reduces equipment investment and improves material utilization, but also achieves better pattern alignment. Furthermore, the instantaneous energy control of the laser protects the integrity of the passivation layer, providing a low-cost, high-precision, and low-damage back contact electrode fabrication solution for TBC solar cells.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a back contact electrode of a TBC solar cell, the method comprising:

[0012] Laser grooving of the anti-reflection layer and chemical deposition of the seed layer are completed simultaneously through laser chemical deposition. Then, a metallized electrode is prepared on the surface of the seed layer to obtain the back contact electrode of the TBC solar cell.

[0013] The laser used in the laser chemical metal deposition is a nanosecond pulsed laser.

[0014] In this invention, TBC solar cell is short for tunneling oxide passivated contact back contact solar cell. It is a high-efficiency crystalline silicon solar cell based on tunneling oxide passivation contact technology, in which both positive and negative metal electrodes are fabricated on the back of the cell. The front of the TBC solar cell is completely free of metal grid lines, which can maximize the utilization of incident light. At the same time, the passivated contact structure on the back can significantly reduce carrier recombination loss, thereby achieving higher photoelectric conversion efficiency.

[0015] In this invention, the back contact electrode of a TBC solar cell refers to the collective term for the p-type and n-type electrodes that are fabricated on the back of a TBC solar cell and arranged in an alternating pattern.

[0016] In the preparation method provided by the present invention, during laser chemical deposition (LCMD), the temperature of the solution and the substrate is raised by nanosecond pulsed laser radiation; when the laser power exceeds a certain threshold, the anti-reflection coating is ablated in the laser irradiation area, wherein the ablation and deposition areas are defined by the laser opening area; in addition, the silicon on the surface is heated by radiation, and the laser generates electron-hole pairs in the solar cell, and the electrons move to the surface, causing the metal to be deposited from the liquid plating bath to the ablated area.

[0017] The preparation method provided by this invention employs laser chemical metal deposition technology, which generates a seed layer in situ while simultaneously etching the anti-reflection layer with laser, eliminating the need for a separate seed layer preparation step. Therefore, the preparation method not only retains the inherent advantages of preparing metallized electrodes, but also directly replaces PVD equipment and subsequent mask etching equipment with laser chemical deposition equipment, thereby saving 70% of equipment investment. Furthermore, it enables the seed layer to be generated in situ only in the gate line area (non-full-area deposition), improving material utilization (material utilization > 90%) and achieving better pattern alignment.

[0018] In the preparation method provided by the present invention, the laser used in the laser chemical metal deposition is a nanosecond pulsed laser. By utilizing the high instantaneous power density and extremely short action time of the pulsed laser, the anti-reflection layer is removed instantaneously without transferring heat to the silicon substrate and passivation layer, thus reducing thermal damage.

[0019] In summary, the fabrication method provided by this invention achieves patterned fabrication of the gate area in one step by simultaneously etching the anti-reflection layer and depositing the seed layer using laser chemical metal deposition and nanosecond pulsed laser. The fabrication method not only significantly reduces equipment investment and improves material utilization, but also achieves better pattern alignment. Furthermore, it protects the integrity of the passivation layer by controlling the instantaneous energy of the laser, providing a low-cost, high-precision, and low-damage back contact electrode fabrication scheme for TBC solar cells.

[0020] Preferably, the nanosecond pulsed laser has a wavelength of 530nm~535nm, a pulse width of 10ns~200ns, a laser spot diameter of 5μm~25μm, a repetition frequency of 1MHz~10MHz, and a power density of 5J / cm². 2 ~15J / cm 2 The scanning speed is 2m / s to 5m / s.

[0021] In this invention, the wavelength of the nanosecond pulsed laser is 530nm~535nm, for example, it can be 530nm, 530.5nm, 531nm, 531.5nm, 532nm, 532.5nm, 533nm, 533.5nm, 534nm, 534.5nm or 535nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] In this invention, the wavelength of the nanosecond pulsed laser is 530nm~535nm. The electrolyte solution has low absorption of this wavelength, while silicon has high absorption of this wavelength, which allows for precise heating and etching of the area.

[0023] In this invention, the pulse width of the nanosecond pulse laser is 10ns to 200ns, for example, it can be 10ns, 20ns, 30ns, 40ns, 50ns, 60ns, 70ns, 80ns, 90ns, 100ns, 120ns, 140ns, 160ns, 180ns or 200ns, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In this invention, the laser spot diameter of the nanosecond pulsed laser is 5μm to 25μm, for example, it can be 5μm, 7μm, 9μm, 11μm, 13μm, 15μm, 17μm, 19μm, 21μm, 23μm or 25μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In this invention, the repetition frequency of the nanosecond pulse laser is 1MHz to 10MHz, for example, it can be 1MHz, 2MHz, 3MHz, 4MHz, 5MHz, 6MHz, 7MHz, 8MHz, 9MHz or 10MHz, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] In this invention, the power density of the nanosecond pulsed laser is 5 J / cm². 2 ~15J / cm 2 For example, it could be 5J / cm 2 6J / cm 2 7J / cm 2 8J / cm2 9J / cm 2 10J / cm 2 11J / cm 2 12J / cm 2 13J / cm 2 14J / cm 2 Or 15J / cm 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0027] In this invention, the scanning speed of the nanosecond pulsed laser is 2m / s to 5m / s, for example, it can be 2m / s, 2.5m / s, 3m / s, 3.5m / s, 4m / s, 4.5m / s or 5m / s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the temperature of the electrolyte solution used in the laser chemical deposition is 15°C to 35°C, for example, it can be 15°C, 17°C, 19°C, 21°C, 23°C, 25°C, 27°C, 29°C, 31°C, 33°C or 35°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the seed layer includes at least one of a copper seed layer, a nickel seed layer, a titanium seed layer, a molybdenum seed layer, or an alloy seed layer, or at least two of them stacked together.

[0030] Preferably, in the laser chemical deposition, the seed layer is thickened by photoinduced chemical plating (LIEP).

[0031] Preferably, the method for preparing the metallized electrode includes sequentially performing copper electroplating, capping layer deposition, and heat treatment.

[0032] Preferably, the components of the electroplating solution used in the copper electroplating include copper sulfate, sulfuric acid, chloride ions, brightener, and inhibitor.

[0033] Preferably, the brightener comprises sodium polydithiopropane sulfonate.

[0034] Preferably, the inhibitor comprises polypropylene oxide and / or ethylene oxide.

[0035] Preferably, the concentration of sulfuric acid in the electroplating solution is 30 g / L to 100 g / L, and the concentration of chloride ions is 50 ppm to 110 ppm.

[0036] In this invention, the concentration of sulfuric acid (H2SO4) in the electroplating solution is 30 g / L to 100 g / L, for example, it can be 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L or 100 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In this invention, the concentration of chloride ions in the electroplating solution is 50ppm to 110ppm, for example, it can be 50ppm, 55ppm, 60ppm, 65ppm, 70ppm, 75ppm, 80ppm, 85ppm, 90ppm, 95ppm, 100ppm, 105ppm or 110ppm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] Preferably, the temperature of the electroplating solution used in the copper electroplating is 15℃~35℃, for example, it can be 15℃, 17℃, 19℃, 21℃, 23℃, 25℃, 27℃, 29℃, 31℃, 33℃ or 35℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the coating layer is deposited by electroplating and / or chemical vapor deposition.

[0040] Preferably, the heat treatment is performed at a temperature of 200℃ to 400℃ for 5 min to 50 min, and in a protective atmosphere.

[0041] In this invention, the temperature of the heat treatment is 200℃~400℃, for example, it can be 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃ or 400℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] In this invention, the heat treatment time is 5 min to 50 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min or 50 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] In this invention, when the heat treatment temperature is 200℃~400℃, a low-resistance metal silicide ohmic contact can be effectively formed, and the damage of high temperature to the battery passivation layer can be suppressed, the contact resistance can be reduced, and a low interfacial recombination rate can be maintained. At the same time, it promotes the recrystallization of copper grains, thereby improving FF and Voc. If the heat treatment temperature is too low, the solid-state reaction between the seed layer metal and the silicon substrate will be incomplete and uneven, resulting in an increase in contact resistance. If the heat treatment temperature is too high, thermal damage will occur, reducing the on-state voltage.

[0044] Preferably, when the material of the covering layer is tin, the temperature of the heat treatment is not higher than 220°C, for example, it can be 180°C, 190°C, 200°C, 210°C or 220°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] In a second aspect, the present invention provides a TBC solar cell back contact electrode, wherein the TBC solar cell back contact electrode is obtained by the preparation method described in the first aspect;

[0046] The back contact electrode of the TBC solar cell includes a seed layer and a metallized electrode covering the surface of the seed layer.

[0047] Preferably, the thickness of the seed layer is 50nm to 200nm, for example, it can be 50nm, 75nm, 100nm, 125nm, 150nm, 175nm or 200nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] In this invention, when the seed layer thickness is 50nm~200nm, a continuous and dense seed layer can be formed, and a uniform metal silicide can be formed during the annealing process, optimizing the carrier transport interface and suppressing the damage to the PN junction caused by excessive metal diffusion, thereby achieving low-resistance ohmic contact and improving the fill factor (FF) and open-circuit voltage (Voc). If the seed layer thickness is too thin, it will result in incomplete seed layer coverage, interruption of the electron transport path, and allow copper ions to diffuse into silicon, damaging the PN junction passivation. If the seed layer thickness is too thick, it will easily lead to gate line detachment, increase material consumption, and reduce material utilization.

[0049] Preferably, the metallized electrode includes a copper layer and a capping layer stacked in a direction away from the seed layer;

[0050] The thickness of the copper layer is 3μm~30μm;

[0051] The thickness of the covering layer is 1μm~5μm;

[0052] The material of the covering layer includes tin, silver, tin alloy, copper alloy or silver alloy.

[0053] In this invention, the cover layer is used to prevent copper layer oxidation and promote the welding of interconnected battery cells. The cover layer also avoids direct contact between the copper layer and the EVA sealant.

[0054] In this invention, the thickness of the copper layer is 3μm to 30μm, for example, it can be 3μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm or 30μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] In this invention, the thickness of the covering layer is 1μm to 5μm, for example, it can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] Thirdly, the present invention provides a TBC solar cell, the TBC solar cell comprising the TBC solar cell back contact electrode described in the second aspect.

[0057] Fourthly, the present invention provides a fabrication process for the TBC solar cell described in the third aspect, the fabrication process comprising:

[0058] The silicon wafer is sequentially polished, subjected to first LP (Laminated Layer) deposition, boron diffusion, first patterning, alkaline etching, second LP deposition, phosphorus diffusion, second patterning, texturing, atomic layer deposition of Al2O3, and front and back films deposition; then the back contact electrode of the TBC solar cell described in the second aspect is prepared using the preparation method described in the first aspect, thus obtaining the TBC solar cell.

[0059] In this invention, the polishing in the preparation process is chemical or chemical mechanical polishing of the silicon wafer surface to remove the cutting damage layer, reduce surface roughness, and obtain a clean and smooth surface.

[0060] In this invention, the first LP step in the fabrication process is the first laser doping treatment. In the first LP step, laser energy is used to drive the doping source to a specific area on the back of the silicon wafer to form a selectively heavily doped p+ region, which lays the foundation for the subsequent fabrication of the boron emitter region of the back contact, thereby facilitating the achievement of excellent ohmic contact.

[0061] In this invention, the boron diffusion process involves the diffusion of boron atoms onto the back side of a silicon wafer to form a p-type doped layer. The boron diffusion process typically employs a solid boron source or a boron-bromine carrier gas at high temperatures, with the aim of constructing a p-type emitter structure for collecting holes in a back-contact battery.

[0062] In this invention, the first patterning step in the fabrication process involves selectively removing the borosilicate glass layer formed after boron diffusion to define the back field contact area. Laser ablation or mask etching techniques are typically used in the first patterning step. Precise patterning facilitates subsequent local contact windowing.

[0063] In this invention, the alkaline etching process involves using an alkaline solution to remove the parasitic doped layer formed on the front and edge of the silicon wafer during phosphorus diffusion, as well as the phosphosilicate glass on the back side. The alkaline etching is used to eliminate edge short-circuit paths and achieve insulation isolation between the n-type and p-type regions on the back side.

[0064] In this invention, the second LP in the preparation process is a second laser doping treatment, which is usually used to perform n-type doping in the gap region between the p-type regions that have been patterned on the back side; the second LP is used to form an n+ heavily doped region, thereby reducing the contact resistance of the n-type region and improving the electron collection efficiency.

[0065] In this invention, the phosphorus diffusion in the preparation process is performed by diffusing phosphorus atoms on the back side of the silicon wafer to form an n-type doped layer.

[0066] In this invention, the second patterning step in the preparation process is to selectively remove the phosphorus silicate glass layer formed after phosphorus diffusion in order to precisely define the n-type contact area on the back side; the second patterning step is used in conjunction with the first patterning step to finally form alternating, mutually insulated p-type and n-type contact windows on the back side.

[0067] In this invention, the texturing process in the preparation process involves forming a micron-level pyramidal textured surface structure on the front side of the battery. The micron-level pyramidal textured surface structure is achieved through anisotropic alkaline solution corrosion, which can effectively trap light and reduce optical reflection loss, thereby significantly increasing the battery's absorption of sunlight and improving the short-circuit current of the TBC solar cell.

[0068] In this invention, the atomic layer deposition of Al2O3 in the preparation process is to deposit an ultra-thin, dense, and conformal aluminum oxide film on the back of the battery; the aluminum oxide film is used to provide field effect passivation, has an excellent passivation effect on the p-type silicon surface, and can effectively suppress carrier recombination, thereby significantly improving the open circuit voltage and efficiency of TBC solar cells.

[0069] In this invention, the front and back film deposition in the fabrication process refers to the deposition of a thin film (front film) on the front side and a thin film (back film) on the back side of the TBC solar cell. The main function of the front film is to reduce reflection and passivate, and it is usually based on silicon nitride. The outermost layer of the back film is an anti-reflection layer.

[0070] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] (1) In the preparation method provided by the present invention, during laser chemical deposition (LCMD), the temperature of the solution and the substrate is raised by nanosecond pulsed laser radiation; when the laser power exceeds a certain threshold, the anti-reflection coating is ablated in the laser irradiation area, wherein the ablation and deposition areas are defined by the laser opening area; in addition, the silicon on the surface is heated by radiation, and the laser generates electron-hole pairs in the solar cell, and the electrons move to the surface, causing the metal to be deposited from the liquid plating bath to the ablated area;

[0073] (2) In the preparation method provided by the present invention, laser chemical metal deposition technology is used to generate a seed layer in situ while laser etching the anti-reflection layer, eliminating the need for a separate seed layer preparation process; therefore, the preparation method not only retains the inherent advantages of preparing metallized electrodes, but also uses laser chemical deposition equipment to directly replace PVD equipment and subsequent mask etching equipment, thereby saving 70% of equipment investment, and also enables the seed layer to be generated in situ only in the gate line area (non-full-area deposition), improving the material utilization rate (material utilization rate >90%), and also enabling better pattern alignment;

[0074] (3) In the preparation method provided by the present invention, the laser used in the laser chemical metal deposition is a nanosecond pulsed laser. By utilizing the high instantaneous power density and extremely short action time of the pulsed laser, the anti-reflection layer is removed instantly without transferring heat to the silicon substrate and passivation layer, thus reducing thermal damage.

[0075] (4) The preparation method provided by the present invention uses laser chemical metal deposition and nanosecond pulsed laser to simultaneously complete the etching of the anti-reflection layer and the in-situ deposition of the seed layer, thereby realizing the patterned preparation of the grid line region in one step. The preparation method not only significantly reduces equipment investment and improves material utilization, but also achieves better pattern alignment. Furthermore, it protects the integrity of the passivation layer by controlling the instantaneous energy of the laser, providing a low-cost, high-precision and low-damage back contact electrode preparation scheme for TBC solar cells. Attached Figure Description

[0076] Figure 1 This is a flowchart of the preparation method of the back contact electrode of the TBC solar cell provided in Examples 1-11.

[0077] Figure 2This is a schematic diagram illustrating the principle of laser chemical deposition in the preparation methods provided in Examples 1-11.

[0078] Among them, 1-antireflective layer; 2-seed layer; 3-electrolyte solution; 4-metal ions; 5-copper layer; 6-capping layer; 7-silicon substrate. Detailed Implementation

[0079] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0080] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0081] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0082] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0083] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0084] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0085] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0086] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0087] Example 1

[0088] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell, such as... Figure 1 As shown, the preparation method includes:

[0089] (1) Through laser chemical deposition (the principle is briefly described in the figure below) Figure 2 As shown), and in conjunction with laser-induced electroless plating (LIEP) to thicken the nickel seed layer 2, the laser grooving of the anti-reflection layer 1 and the chemical deposition of the nickel seed layer 2 are completed simultaneously;

[0090] The laser used in the laser chemical metal deposition is a nanosecond pulsed laser with a wavelength of 532 nm, a pulse width of 50 ns, a laser spot diameter of 15 μm, a repetition frequency of 5 MHz, and a power density of 10 J / cm². 2 The scanning speed is 3 m / s;

[0091] The temperature of the electrolyte solution 3 used in the laser chemical deposition is 25°C; the electrolyte solution 3 used in the laser chemical deposition is a NiSO4 solution with a nickel ion concentration of 75 mmol / L and a pH of 5.

[0092] (2) After electroplating copper and tin on the surface of the nickel seed layer 2 obtained in step (1), the copper layer 5 and Cu-Sn alloy layer (covering layer 6) are formed by sintering at 180°C for 10 min.

[0093] Then, the back contact electrode of the TBC solar cell is obtained by heat treatment at 200°C for 30 minutes in a nitrogen atmosphere.

[0094] The electroplating solution used in the copper electroplating process comprises CuSO4 at a concentration of 128 g / L, sulfuric acid at a concentration of 50 g / L, chloride ions at a concentration of 60 ppm, a brightener (sodium polydisulfide dipropane sulfonate) at a volume concentration of 5 ml / L, and an inhibitor (polypropylene oxide) at a volume concentration of 3 ml / L. The temperature of the electroplating solution is 25°C, and the copper electroplating time is 15 min.

[0095] The electroplating of tin in the tin methanesulfonate system (Sn 2+ The experiment was conducted at a concentration of 40 g / L and an acidity of 100 g / L, with a current density of 2 A / dm³. 2 The deposition time was 3 minutes.

[0096] This embodiment also provides a TBC solar cell back contact electrode, which is obtained by the above-described preparation method;

[0097] The TBC solar cell back contact electrode includes a nickel seed layer 2 with a thickness of 150 nm and a metallized electrode covering the surface of the nickel seed layer 2.

[0098] The metallized electrode includes a copper layer 5 with a thickness of 10 μm and a Cu-Sn alloy layer (capping layer 6) with a thickness of 3 μm stacked in a direction away from the nickel seed layer 2.

[0099] Example 2

[0100] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell, such as... Figure 1 As shown, the preparation method includes:

[0101] (1) Through laser chemical deposition (the principle is briefly described in the figure below) Figure 2 As shown), and in conjunction with laser-induced electroless plating (LIEP) to thicken the copper seed layer 2, the laser grooving of the anti-reflection layer 1 and the chemical deposition of the copper seed layer 2 are completed simultaneously.

[0102] The laser used in the laser chemical metal deposition is a nanosecond pulsed laser with a wavelength of 532 nm, a pulse width of 10 ns, a laser spot diameter of 25 μm, a repetition frequency of 10 MHz, and a power density of 5 J / cm². 2 The scanning speed is 5 m / s;

[0103] The temperature of the electrolyte solution 3 used in the laser chemical deposition is 35°C; the electrolyte solution 3 used in the laser chemical deposition is a NiSO4 solution with a nickel ion concentration of 75 mmol / L and a pH of 5.

[0104] (2) Electroplating of copper and silver coating layers are performed sequentially on the surface of the copper seed layer 2 obtained in step (1);

[0105] Then, the back contact electrode of the TBC solar cell is obtained by heat treatment at 300°C for 50 minutes in an argon atmosphere.

[0106] The electroplating solution used in the copper electroplating process comprises CuSO4 at a concentration of 128 g / L, sulfuric acid at a concentration of 100 g / L, chloride ions at a concentration of 110 ppm, a brightener (sodium polydithiopropane sulfonate) at a volume concentration of 5 ml / L, and an inhibitor (ethylene oxide) at a volume concentration of 3 ml / L; the temperature of the electroplating solution is 35°C.

[0107] The silver capping layer was deposited using chemical vapor deposition.

[0108] This embodiment also provides a TBC solar cell back contact electrode, which is obtained by the above-described preparation method;

[0109] The back contact electrode of the TBC solar cell includes a copper seed layer 2 with a thickness of 50 nm and a metallized electrode covering the surface of the copper seed layer 2.

[0110] The metallized electrode comprises a copper layer 5 with a thickness of 30 μm and a silver capping layer 6 with a thickness of 1 μm, stacked along a direction away from the copper seed layer 2.

[0111] Example 3

[0112] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell, such as... Figure 1 As shown, the preparation method includes:

[0113] (1) Through laser chemical deposition (the principle is briefly described in the figure below) Figure 2 As shown), and in conjunction with laser-induced electroless plating (LIEP) to thicken the copper seed layer 2, the laser grooving of the anti-reflection layer 1 and the chemical deposition of the copper seed layer 2 are completed simultaneously.

[0114] The laser used in the laser chemical metal deposition is a nanosecond pulsed laser with a wavelength of 532 nm, a pulse width of 200 ns, a laser spot diameter of 5 μm, a repetition frequency of 1 MHz, and a power density of 15 J / cm². 2 The scanning speed is 2 m / s;

[0115] The temperature of the electrolyte solution 3 used in the laser chemical deposition is 15°C; the electrolyte solution 3 used in the laser chemical deposition is a NiSO4 solution with a nickel ion concentration of 75 mmol / L and a pH of 5.

[0116] (2) After electroplating copper and depositing copper alloy capping layer on the surface of the copper seed layer 2 obtained in step (1);

[0117] Then, the back contact electrode of the TBC solar cell is obtained by heat treatment at 400°C for 5 minutes in a nitrogen atmosphere.

[0118] The electroplating solution used in the copper electroplating process comprises CuSO4 at a concentration of 128 g / L, sulfuric acid at a concentration of 30 g / L, chloride ions at a concentration of 50 ppm, a brightener (sodium polydisulfide dipropane sulfonate) at a volume concentration of 5 ml / L, and an inhibitor (polypropylene oxide) at a volume concentration of 3 ml / L; the temperature of the electroplating solution is 15°C.

[0119] The copper alloy capping layer was deposited using chemical vapor deposition.

[0120] This embodiment also provides a TBC solar cell back contact electrode, which is obtained by the above-described preparation method;

[0121] The TBC solar cell back contact electrode includes a copper seed layer 2 with a thickness of 200 nm and a metallized electrode covering the surface of the copper seed layer 2.

[0122] The metallized electrode includes a copper layer 5 with a thickness of 3 μm and a copper alloy capping layer 6 with a thickness of 5 μm, which are stacked in a direction away from the copper seed layer 2.

[0123] Example 4

[0124] This embodiment provides a method for fabricating the back contact electrode of a TBC solar cell, except that the power density of the nanosecond pulsed laser is 2 J / cm². 2 Except for the above, everything else is the same as in Example 1.

[0125] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0126] Example 5

[0127] This embodiment provides a method for fabricating the back contact electrode of a TBC solar cell, except that the power density of the nanosecond pulsed laser is 25 J / cm². 2 Except for the above, everything else is the same as in Example 1.

[0128] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0129] Example 6

[0130] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell. Except for the pulse width of the nanosecond pulsed laser being 2ns, the rest is the same as in Embodiment 1.

[0131] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0132] Example 7

[0133] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell. Except for the pulse width of the nanosecond pulsed laser being 250 ns, the rest is the same as in Embodiment 1.

[0134] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0135] Example 8

[0136] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell, which is the same as that in Embodiment 1.

[0137] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the thickness of the nickel seed layer 2 in the TBC solar cell back contact electrode is 20 nm.

[0138] Example 9

[0139] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell, which is the same as that in Embodiment 1.

[0140] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the thickness of the nickel seed layer 2 in the TBC solar cell back contact electrode is 280nm.

[0141] Example 10

[0142] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell. Except for the heat treatment temperature of 150°C in step (2), the rest is the same as in embodiment 1.

[0143] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0144] Example 11

[0145] This embodiment provides a method for preparing the back contact electrode of a TBC solar cell. Except for the heat treatment temperature of 500°C in step (2), the rest is the same as in embodiment 1.

[0146] This embodiment also provides a TBC solar cell back contact electrode, which is the same as in Embodiment 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this embodiment.

[0147] Comparative Example 1

[0148] This comparative example provides a method for fabricating the back contact electrode of a TBC solar cell, except that the laser used in the laser chemical metal deposition is a continuous wave laser with a wavelength of 532 nm, a laser spot diameter of 15 μm, and a power density of 10 J / cm². 2 Except for the scanning speed of 2m / s, everything else is the same as in Example 1.

[0149] This comparative example also provides a TBC solar cell back contact electrode, which is identical to Example 1 except that the TBC solar cell back contact electrode is obtained by the preparation method provided in this comparative example.

[0150] Comparative Example 2

[0151] This comparative example provides a method for preparing the back contact electrode of a TBC solar cell. The preparation method is a screen printing silver paste process. The screen printing silver paste process is as follows: an electrode pattern is formed on the surface of the anti-reflective layer on the back by screen printing silver paste, dried at 180°C, and then sintered at 850°C to form an ohmic contact.

[0152] Comparative Example 3

[0153] This comparative example provides a method for preparing the back contact electrode of a TBC solar cell. The preparation method is a PVD seed layer deposition + copper electroplating process. Specifically, a copper seed layer is deposited on the surface of the anti-reflection layer on the back side by physical vapor deposition (PVD), and then copper is electroplated on the copper seed layer to form a full-surface metal contact.

[0154] Comparative Example 4

[0155] This comparative example provides a method for fabricating the back contact electrode of a TBC solar cell. The fabrication method is a three-step process of laser patterning, PVD seed layer deposition, and copper electroplating. Specifically, the electrode pattern is first defined by laser etching of an anti-reflection layer, then a copper seed layer is deposited by PVD, and finally copper is electroplated on the copper seed layer to form the grid line electrode.

[0156] The n-type silicon wafer (silicon substrate 7) undergoes the following sequential processes: double-sided polishing, first LPCVD deposition of a polycrystalline silicon layer, boron diffusion, patterning of the N-region, alkaline etching, second LPCVD deposition of a polycrystalline silicon layer, phosphorus diffusion, patterning of the P-region, front-side texturing (alkaline etching), ALD deposition of an Al2O3 passivation layer, and PECVD deposition of the front-side SiN. x Anti-reflective layer 1 and back SiN x Anti-reflection layer 1; then, using the preparation methods provided in the above embodiments and comparative examples, the back contact electrode of the TBC solar cell provided in the above embodiments and comparative examples is prepared, and the TBC solar cell is obtained.

[0157] The electrical performance of the obtained TBC solar cells was tested under standard test conditions (AM1.5G spectrum, 1000W / m²). 2 Under irradiance (cell temperature 25℃), the current-voltage characteristic curves of the TBC solar cells were measured using a solar simulator and IV test system. The conversion efficiency (Eta), open circuit voltage (Uoc), short circuit current (Isc), fill factor (FF), series resistance (Rser), and parallel resistance (RshuntDfDr) of the TBC solar cells are shown in Table 1.

[0158] Table 1

[0159]

[0160] From Table 1, we can obtain:

[0161] (1) In this invention, when preparing TBC solar cells, the back contact electrode of TBC solar cells is prepared using the preparation methods provided in Examples 1 to 3, and the resulting TBC solar cells exhibit superior overall electrical performance.

[0162] (2) By comparing Example 1 with Examples 4 and 5, it can be seen that the power density of the nanosecond pulsed laser in this invention is 5 J / cm². 2 ~15J / cm 2 At this time, TBC solar cells exhibit better overall electrical performance. This is because the power density range can effectively ablate the anti-reflection layer 1 and drive the reduction deposition of metal ions 4, while avoiding thermal damage to the silicon wafer passivation layer caused by excessive energy. If the power density is too low, it will lead to incomplete ablation or discontinuous deposition. If the power density is too high, it will damage the passivation layer.

[0163] (3) By comparing Example 1 with Examples 6 and 7, it can be seen that in this invention, when the pulse width of the nanosecond pulse laser is 10ns~200ns, the TBC solar cell exhibits better overall electrical performance. This is because the pulse width range can achieve extremely high instantaneous power, ensuring that energy acts on the anti-reflection layer 1 in a very short time and is instantly vaporized and removed, while the heat does not have time to diffuse to the surrounding silicon substrate 7 and passivation layer, thereby minimizing thermal damage, protecting the passivation effect, and helping to obtain a high open circuit voltage.

[0164] (4) By comparing Example 1 with Examples 8 and 9, it can be seen that in the present invention, when the thickness of the seed layer 2 in the back contact electrode of the TBC solar cell is 50nm~200nm, a continuous and dense seed layer 2 can be formed, and a uniform metal silicide can be formed during the annealing process, which optimizes the carrier transport interface and suppresses the damage of excessive metal diffusion to the PN junction, thereby achieving low-resistance ohmic contact and improving the fill factor (FF) and open-circuit voltage (Voc). If the thickness of the seed layer 2 is too thin, it will result in incomplete coverage of the seed layer 2, interruption of the electron transport path, and diffusion of copper ions into silicon, which will damage the passivation of the PN junction. If the thickness of the seed layer 2 is too thick, it will easily cause the grid line to fall off, increase material consumption, and reduce material utilization.

[0165] (5) By comparing Example 1 with Examples 10 and 11, it can be seen that in the preparation method of the present invention, when the heat treatment temperature is 200℃~400℃, a low-resistance metal silicide ohmic contact can be effectively formed, and the damage of high temperature to the battery passivation layer can be suppressed, the contact resistance can be reduced, and a low interface recombination rate can be maintained. At the same time, it promotes the recrystallization of copper grains, thereby improving FF and Voc. If the heat treatment temperature is too low, the solid-phase reaction between the seed layer 2 metal and the silicon substrate 7 will be incomplete and uneven, resulting in an increase in contact resistance. If the heat treatment temperature is too high, thermal damage will occur, reducing the on-state voltage.

[0166] (6) By comparing Example 1 with Comparative Examples 1 to 4, it can be seen that in the preparation method provided by the present invention, during laser chemical deposition, the temperature of the solution and the substrate is raised by nanosecond pulsed laser radiation; when the laser power exceeds a certain threshold, the anti-reflection coating is ablated in the laser irradiation area, wherein the ablation and deposition areas are defined by the laser opening area; in addition, the silicon on the surface is heated by radiation, and the laser generates electron-hole pairs in the solar cell, and the electrons move to the surface, causing the metal to be deposited from the liquid plating bath to the ablated area;

[0167] The preparation method provided by this invention employs laser chemical metal deposition technology, which simultaneously generates a seed layer 2 in situ while laser etching the anti-reflection layer 1, eliminating the need for a separate seed layer 2 preparation step. Therefore, the preparation method not only retains the inherent advantages of preparing metallized electrodes, but also directly replaces the PVD equipment and subsequent mask etching equipment with laser chemical deposition equipment, thereby saving 70% of equipment investment. Furthermore, it enables the seed layer 2 to be generated in situ only in the gate line region (non-full-area deposition), improving material utilization (material utilization > 90%) and achieving better pattern alignment.

[0168] In the preparation method provided by the present invention, the laser used in the laser chemical metal deposition is a nanosecond pulsed laser. By utilizing the high instantaneous power density and extremely short action time of the pulsed laser, the anti-reflection layer 1 is removed instantaneously without transferring heat to the silicon substrate 7 and the passivation layer, thereby reducing thermal damage.

[0169] In summary, the fabrication method provided by this invention achieves patterned fabrication of the gate area in one step by simultaneously etching the antireflection layer 1 and depositing the seed layer 2 using laser chemical metal deposition and nanosecond pulsed laser. This fabrication method not only significantly reduces equipment investment and improves material utilization, but also achieves better pattern alignment. Furthermore, it protects the integrity of the passivation layer by controlling the instantaneous energy of the laser, providing a low-cost, high-precision, and low-damage back contact electrode fabrication scheme for TBC solar cells.

[0170] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a back contact electrode for a TBC solar cell, characterized in that, The preparation method includes: Laser grooving of the anti-reflection layer and chemical deposition of the seed layer are completed simultaneously through laser chemical deposition. Then, a metallized electrode is prepared on the surface of the seed layer to obtain the back contact electrode of the TBC solar cell. The laser used in the laser chemical metal deposition is a nanosecond pulsed laser.

2. The preparation method according to claim 1, characterized in that, The nanosecond pulsed laser has a wavelength of 530nm~535nm, a pulse width of 10ns~200ns, a laser spot diameter of 5μm~25μm, a repetition frequency of 1MHz~10MHz, and a power density of 5J / cm². 2 ~15J / cm 2 The scanning speed is 2m / s to 5m / s.

3. The preparation method according to claim 1, characterized in that, The temperature of the electrolyte solution used in the laser chemical deposition is 15℃~35℃.

4. The preparation method according to claim 1, characterized in that, In the laser chemical deposition, the seed layer is thickened by photo-induced chemical plating.

5. The preparation method according to claim 1, characterized in that, The method for preparing the metallized electrode includes sequentially performing copper electroplating, capping layer deposition, and heat treatment.

6. The preparation method according to claim 5, characterized in that, The heat treatment is carried out at a temperature of 200℃ to 400℃ for 5 min to 50 min, and in a protective atmosphere.

7. A back contact electrode for a TBC solar cell, characterized in that, The back contact electrode of the TBC solar cell is obtained by the preparation method according to any one of claims 1 to 6; The back contact electrode of the TBC solar cell includes a seed layer and a metallized electrode covering the surface of the seed layer.

8. The back contact electrode of the TBC solar cell according to claim 7, characterized in that, The thickness of the seed layer is 50nm~200nm.

9. The back contact electrode of the TBC solar cell according to claim 7 or 8, characterized in that, The metallized electrode includes a copper layer and a capping layer stacked in a direction away from the seed layer; The thickness of the copper layer is 3μm~30μm; The thickness of the covering layer is 1μm~5μm; The material of the covering layer includes tin, silver, tin alloy, copper alloy or silver alloy.

10. A TBC solar cell, characterized in that, The TBC solar cell includes the TBC solar cell back contact electrode as described in any one of claims 7 to 9.

Images