A thick film paste composition, method of manufacture and use thereof

Abstract

The thick film paste composition provided in the application adopts a lead-selenium-oxide system. Selenium oxide has moderate and controllable chemical corrosion rate on passivation layer materials such as Te oxide or Si oxide, but has extremely weak corrosion on an ultrathin (tunneling oxide layer). During the baking process, the glass powder softens and flows, preferentially reacts with the upper passivation layer and etches it to form a contact window. When the glass material contacts the lower tunneling oxide layer, the corrosion reaction spontaneously stops or is greatly inhibited due to low chemical affinity and insufficient reactivity, which achieves 'zero damage' or 'low damage' to the tunneling oxide layer, and improves the photoelectric conversion efficiency. In addition, the application also provides a preparation method and application of the thick film paste composition.

Description

Technical Field

[0001] This application relates to the field of electronic materials technology, and in particular to a thick film paste composition, its preparation method, and its application. Background Technology

[0002] Crystalline silicon solar cells are the mainstream product in the photovoltaic power generation market. With technological advancements, traditional P-type silicon cells are gradually approaching their theoretical efficiency limits, while N-type cells, due to their higher minority carrier lifetime and lack of light-induced degradation, are becoming the mainstream direction for next-generation high-efficiency cells. Currently, the mainstream technology in the market is accelerating its shift towards N-type cells, especially tunneling oxide passivated contact (TOPCon) cells and interdigitated back contact (BC) cells.

[0003] Both TOPCon and BC cell structures typically contain a multilayer film structure on the back side or in the electrode contact area: a tunneling oxide layer + a doped polycrystalline silicon layer (poly-Si) + a passivation layer. The tunneling oxide layer (usually ultrathin) The top passivation layer (such as a doped polysilicon layer) is crucial for achieving passivated contacts. It allows majority carriers to tunnel through while effectively blocking minority carriers, resulting in extremely low surface recombination rates. The doped polysilicon layer on top provides conductive channels and field-effect passivation. , (etc.) are used to further reduce surface lamination and as an anti-reflective layer or protective layer.

[0004] In this battery structure, the conductive electrodes (typically formed by screen-printing and then sintering a metal paste) need to penetrate the top passivation layer to form a good ohmic contact with the underlying polycrystalline silicon layer to ensure effective carrier collection. However, this process places extremely stringent requirements on the etching performance of the paste: the paste must have sufficient penetration power to etch through the dense passivation layer, but it cannot over-penetrate and must strictly avoid penetrating the underlying tunneling oxide layer. Once the tunneling oxide layer is damaged, it will lead to severe carrier recombination, significantly reducing the open-circuit voltage and fill factor of the battery, ultimately resulting in a decrease in photoelectric conversion efficiency.

[0005] In existing technologies, the design of thick-film conductive pastes mainly follows the formulation system of silver paste for the front side of P-type silicon solar cells. The silver paste for the front side of P-type cells needs to penetrate the silicon nitride antireflection layer to directly form an ohmic contact with the underlying P-type emitter (crystalline silicon). This formulation system exhibits significant incompatibility with multilayer film structures of TOPCon or BC cells (especially those with ultrathin tunneling oxide layers). In practical applications, using the P-type formulation often leads to two main problems: first, insufficient etching capability of the glass system results in incomplete etching of the passivation layer and high contact resistance; second, the glass system reacts too violently, causing uncontrolled etching depth that penetrates the tunneling oxide layer, which should be strictly protected, leading to increased recombination current. Both of these situations directly result in lower-than-expected photoelectric conversion efficiency of the cell, limiting the performance of high-efficiency N-type cells.

[0006] Therefore, developing a thick film slurry composition specifically suitable for N-type battery structures, capable of selectively penetrating the passivation layer and forming good contact with the polycrystalline silicon layer, while not damaging the tunneling oxide layer, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In view of this, the present invention provides a thick film paste composition that can selectively penetrate the passivation layer and form good contact with the polycrystalline silicon layer without damaging the tunneling oxide layer, thereby improving its photoelectric conversion efficiency.

[0008] To solve the above problems, this application adopts the following technical solution:

[0009] One objective of this application is to provide a thick film paste composition comprising:

[0010] a) A conductive metal or its derivative, comprising 75-95 wt% based on the total solids in the composition;

[0011] b) Lead-selenium glass powder, on a solids basis, comprising 0.5-15 wt%; wherein the lead-selenium glass powder contains 30-90 wt% lead oxide and 10-70 wt% selenium oxide; and

[0012] c) Organic media.

[0013] In some embodiments, the conductive metal includes silver.

[0014] In some embodiments, the content of the conductive metal or its derivative is 90-95 wt% of the total solids.

[0015] In some embodiments, the softening point temperature of the lead-selenium glass powder is correlated with its melting temperature, enabling it to etch through the insulating film during calcination, but not substantially through the tunneling oxide layer.

[0016] In some embodiments, the lead-selenium glass powder has a particle size range of 1.0 micrometer to 3.0 micrometer.

[0017] In some embodiments, the melting temperature of the lead-selenium glass powder is 450°C-650°C.

[0018] In some embodiments, the composition further comprises one or more additives selected from the group consisting of: .

[0019] In some embodiments, the organic medium includes a polymer resin and an organic solvent.

[0020] In some embodiments, the organic medium further includes one or more additives selected from the group consisting of stabilizers, surfactants, and thickeners.

[0021] The second objective of this application is to provide a method for preparing the aforementioned thick film paste composition, comprising the following steps:

[0022] Preparation of lead-selenium-based glass powder: Mix raw materials containing 30-90 wt% lead oxide and 10-70 wt% selenium oxide, melt at 450℃-650℃, then quench and pulverize to obtain glass powder;

[0023] Preparation of organic media: Mixing polymer resin with organic solvent;

[0024] Mixing and dispersing: The conductive metal or its derivative, the lead-selenium glass powder and the organic medium are mixed and then rolled and dispersed evenly to obtain a thick film paste composition.

[0025] The third objective of this application is to provide a semiconductor electrode, which is formed on a semiconductor substrate by printing, drying and calcining the thick film paste composition.

[0026] The fourth objective of this application is to provide a semiconductor article, comprising:

[0027] Semiconductor substrate;

[0028] One or more insulating films formed on at least one surface of the semiconductor substrate;

[0029] The semiconductor electrode formed on the one or more insulating films;

[0030] The electrode penetrates one or more insulating films to form an ohmic contact with the polycrystalline silicon layer located beneath the insulating films, and substantially does not penetrate the tunneling oxide layer located beneath the polycrystalline silicon layer.

[0031] In some embodiments, the semiconductor product is an N-type solar cell.

[0032] In some embodiments, the N-type solar cell is a TOPCon cell or a BC cell.

[0033] The fifth objective of this application is to provide an application of the aforementioned thick film paste composition in the manufacture of semiconductor products, wherein the composition is used to form a conductive electrode that can form an ohmic contact with a polycrystalline silicon layer through one or more insulating films deposited on a semiconductor substrate, while maintaining a barrier to the tunneling oxide layer.

[0034] The present application adopts the above technical solution, and its beneficial effects are as follows:

[0035] The thick film paste composition provided in this application employs a lead-selenium oxide system, wherein the lead-selenium glass powder contains 30-90% lead oxide and 10-70% selenium oxide. Compared to tellurium oxide or silicon oxide, selenium oxide has advantages over lead oxide and silicon oxide in... , The chemical corrosion rate of passivation layer materials is moderate and controllable, but for ultrathin layers... The corrosiveness of the (tunneling oxide layer) is extremely low. During calcination, the glass powder softens and flows, preferentially reacting with and etching open the upper SiNx passivation layer to form contact windows. When the glass material comes into contact with the underlying tunneling oxide layer, the corrosion reaction spontaneously stops or is greatly inhibited due to low chemical affinity and insufficient reactivity. This achieves "zero damage" or "low damage" to the tunneling oxide layer, improving photoelectric conversion efficiency. Detailed Implementation

[0036] The embodiments of this application are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to reference are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer", etc., indicating orientation or positional relationship are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. In this invention, all raw materials are commercially available, and all equipment used is conventional equipment in the art. Unless otherwise stated, all percentages mentioned in this invention are weight percentages.

[0040] The present invention provides a thick film paste composition for forming electrodes in a semiconductor article, the semiconductor article comprising a semiconductor substrate, the semiconductor substrate including one or more insulating films deposited on at least one surface thereon;

[0041] The thick film paste composition comprises:

[0042] a) A conductive metal or its derivative, comprising 75-95 wt% based on the total solids in the composition;

[0043] b) Lead-selenium glass powder, on a solids basis, having a content of 0.5-15 wt%; the lead-selenium glass powder contains 30-90 wt% lead oxide and 10-70 wt% selenium oxide;

[0044] c) Organic media;

[0045] The electrode formed by calcining the thick film paste composition can pass through one or more insulating films and form an ohmic contact with the polycrystalline silicon layer located below the insulating film, while maintaining a barrier to the tunneling oxide layer in the semiconductor substrate.

[0046] It is understood that in this embodiment, the lead-selenium glass powder contains 30-90% lead oxide and 10-70% selenium oxide. Selenium oxide exhibits strong reactivity at high temperatures and can react with… , When the passivation layer material undergoes a chemical reaction (generating volatile products or low-melting-point eutectic), it effectively "penetrates" or etches open these dense insulating films, creating contact windows for the conductive metal. Compared to traditional lead-silicon or lead-telluride glasses, lead-selenium glasses are more suitable for ultra-thin... The chemical corrosion rate is extremely low. Selenium oxides and The reaction exhibits a relatively small change in Gibbs free energy and insufficient thermodynamic driving force. Therefore, when the glass frit etches through the passivation layer and contacts the underlying tunneling oxide layer, the corrosion reaction spontaneously terminates, achieving precise control of "penetrating the upper passivation layer but not the lower tunneling oxide layer." The integrity of the tunneling oxide layer is preserved, thus maintaining its function of blocking minority carriers and avoiding voltage loss caused by metal-induced recombination centers.

[0047] Furthermore, the melting temperature of the lead-selenium glass powder is 450℃-650℃.

[0048] It should be noted that the melting temperature of the glass powder is 450℃-650℃, which means that the glass powder has a low softening point and melting temperature. During the battery sintering process (typically with a peak temperature of ~750℃), the glass melt has a moderate viscosity and surface tension. This ensures that the molten glass can effectively flow and wet the silver powder and passivation layer to complete the etching, while preventing excessive fluidity due to low viscosity, which could allow it to penetrate through pinholes or grain boundaries and damage the underlying tunneling oxide layer.

[0049] In some embodiments, the conductive metal includes silver.

[0050] It is understandable that during the high-temperature sintering stage, some silver will dissolve in the molten lead-selenium glass. During the cooling process, as the solubility of silver in the glass decreases, silver will precipitate from the glass in the form of microcrystals or nanoparticles and grow directly on the exposed polycrystalline silicon. The surface of the polysilicon layer is directly contacted via a silver-induced epitaxial growth mechanism, forming a direct silver / polysilicon interface. Due to the heavy doping of the polysilicon layer, this interface readily forms an ohmic contact, significantly reducing the contact resistance (Rc).

[0051] Furthermore, since the glass layer is confined to the contact region and the tunneling oxide layer remains intact, the passivation contact structure between the polycrystalline silicon and the silicon substrate remains undamaged. The minority carrier recombination rate (J0,metal) in the metal contact region is significantly reduced, directly contributing to the increase in the cell open-circuit voltage (Voc).

[0052] In some embodiments, the content of the conductive metal or its derivative is 90-95 wt% of the total solids.

[0053] It is understandable that the high silver content (75-95 wt%) ensures extremely low bulk resistivity of the electrode itself; the excellent ohmic contact between silver and polycrystalline silicon ensures extremely low interfacial contact resistance. The series resistance (Rs) of the cell decreases significantly, thereby improving the fill factor (FF); furthermore, due to the "zero-damage" characteristic of lead-selenium glass to the tunneling oxide layer, the passivation structure of the cell is almost unaffected by the metallization process. The dark saturation current density (J0) of the cell remains at a low level, and the open-circuit voltage (Voc) is maintained or even slightly increased. Under the dual effects of maintaining / increasing Voc and improving FF, the absolute photoelectric conversion efficiency of the cell achieves a significant improvement of approximately 0.1%. In the photovoltaic industry, a 0.1% efficiency gain has extremely high commercial value.

[0054] Furthermore, since the melting temperature of the glass powder is only 450℃-650℃, far lower than the 800℃-1200℃ of traditional glass powder, this significantly reduces energy consumption and production costs during the glass melting process, aligning with the trend of green manufacturing. The introduction of organic media (including polymers, solvents, and additives) gives the composition suitable rheological properties, meeting the requirements of fine-line screen printing, ensuring high-precision patterning on solar cells, reducing the light-blocking area, and further improving the short-circuit current (Jsc).

[0055] The thick film paste composition provided by this invention achieves targeted penetration of the multilayer film structure of N-type batteries through low-melting-point lead-selenium glass powder, effectively etching the upper layer. / The passivation layer forms a low-resistance ohmic contact and perfectly protects the underlying tunneling oxide layer from damage, ultimately improving the photoelectric conversion efficiency of the battery (especially Voc and FF), while also having the advantage of low-energy manufacturing.

[0056] Furthermore, the softening point temperature of the lead-selenium glass powder is related to its melting temperature, enabling it to etch through the insulating film during the calcination process, but not substantially penetrate the tunneling oxide layer.

[0057] It is important to note that during the rapid sintering process of solar cells (typically heating up within seconds), the time window for the reactions of various materials is extremely critical. The softening point of glass powder is intrinsically related to its melting temperature. Lower melting temperatures (450℃-650℃) mean a relatively loose glass network structure, and its softening point (Tg) is correspondingly within a relatively low and controllable range. In the initial stage of heating in the sintering furnace, when the temperature reaches this specific range, the glass powder begins to soften precisely, and its viscosity decreases. This ensures that the glass has sufficient time to pre-wet and begin reacting with the upper layers before the peak temperature is reached. or The passivation film undergoes a chemical reaction. This avoids "reaction lag" caused by an excessively high softening point, where the temperature has reached its peak but the glass has not been effectively etched, resulting in poor contact; it also avoids "reaction advance" caused by an excessively low softening point, where the glass has already flowed excessively before reaching the target temperature, which may cause uncontrollable lateral diffusion.

[0058] Furthermore, since the softening point is related to the melting temperature, the viscosity change curve of the glass melt is smooth and predictable throughout the high-temperature region. The glass melt can continuously etch the passivation layer at a moderate rate until it is completely penetrated, and upon contact with the tunneling oxide layer, the etching reaction naturally slows down or stops due to changes in chemical affinity and the melt's own state (such as changes in surface tension).

[0059] In this embodiment, the softening point associated with the melting temperature determines the final viscosity of the glass at the peak temperature. If the glass powder melting temperature is too high (such as with conventional P-type slurry), its high-temperature viscosity may be too low, resulting in excessive fluidity. In this scheme, glass melted at 450-650°C maintains appropriate viscosity and surface tension at the sintering peak temperature. This physical state makes it difficult for the glass melt to further wet and penetrate the dense passivation layer and reach the ultrathin tunneling oxide layer (~1.5 nm). The layer forms a microstructure where etching stops once it penetrates the passivation layer, thus preserving the integrity and thickness of the tunneling oxide layer and maintaining its band blocking effect on minority carriers.

[0060] Furthermore, overly vigorous glass systems often cause imbalances in element diffusion at the interface, forming voids, or directly penetrating the tunneling layer, leading to direct contact between the metal and the silicon substrate. This feature controls the thermal behavior of the glass, making the interfacial reaction more moderate and uniform, ensuring that the contact interface is a dense silver / polycrystalline silicon layer, rather than a destructive silver / silicon alloying region.

[0061] Because the thermal behavior of glass (softening, flow, reaction) closely matches the sintering process curve and is relatively mild, its sensitivity to the peak sintering temperature is reduced. Even with sintering temperature fluctuations of ±20°C, this composition can still stably achieve the goal of "penetrating the passivation layer without damaging the tunneling layer." This significantly improves the yield and stability during battery mass production.

[0062] Furthermore, the controllable softening flow characteristics mean that the glass's etching capability is released gradually. Regardless of whether the passivation layer is too thick or too thin, the glass system can self-regulate through its inherent thermal behavior to ensure just the right amount of penetration. This avoids over-etching due to a thin passivation layer or under-etching due to a thick passivation layer.

[0063] The control of the aforementioned microscopic processes is ultimately reflected in the macroscopic electrical parameters of the battery as follows:

[0064] Open-circuit voltage (Voc) stability: Since the tunneling oxide layer is "virtually non-penetrating", recombination at the metal / silicon interface is suppressed, and the Voc of the battery will not decrease significantly due to the metallization process, and may even increase slightly due to contact optimization.

[0065] Improved fill factor (FF): "Timely" etching ensures that the contact window is fully opened, silver makes good contact with polysilicon, and low contact resistance, thereby improving FF.

[0066] Reduced leakage current: This avoids localized leakage channels caused by glass penetration of the tunneling layer or silver spike puncture, resulting in a reduction in the reverse leakage current of the battery and an increase in the parallel resistance (Rsh).

[0067] This embodiment establishes an intrinsic relationship between the thermal properties (softening point) of glass powder and the preparation process (melting temperature), endowing the slurry with intelligent response characteristics during rapid sintering—initiating etching at the correct time and stopping etching at the correct interface, thereby realizing changes to the multilayer film structure at the microscale, ultimately ensuring the high voltage, low resistance, and high yield required for high-efficiency N-type batteries.

[0068] In this embodiment, the particle size range of the lead-selenium glass powder is 1.0 micrometer to 3.0 micrometer.

[0069] Understandably, this particle size range ensures uniform dispersion of the glass powder in the slurry, and that each glass particle forms a uniformly sized etch pit during sintering. This creates a uniform and dense contact interface, preventing over-etching (penetrating the tunneling layer) caused by large glass particles or under-etching (poor contact) caused by particles that are too small.

[0070] Furthermore, the composition also comprises one or more additives selected from the group consisting of: .

[0071] It is understood that by introducing the aforementioned additives (such as...) , , (etc.), which can further fine-tune the thermal expansion coefficient, chemical stability or conductivity of the glass, so that it can adapt to passivation layers and polycrystalline silicon layers prepared by different manufacturers and under different process conditions, thus broadening the application window of the product.

[0072] Furthermore, the organic medium includes a polymer resin and an organic solvent.

[0073] Specifically, polymer resins include ethyl cellulose, acrylic resins, nitrocellulose, phenolic resins, and alkyd resins.

[0074] Organic solvents include alcohol esters (such as diethylene glycol monobutyl ether acetate, propylene glycol methyl ether acetate (PMA)), alcohol ethers (such as diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol monoethyl ether (ethyl carbitol), dipropylene glycol monomethyl ether, etc.), terpineol, tributyl citrate, dibutyl phthalate, etc.

[0075] Furthermore, the organic medium also includes one or more additives selected from the group consisting of stabilizers, surfactants, and thickeners.

[0076] Specifically, surfactants include nonionic surfactants (such as alkylphenol polyoxyethylene ethers (OP series), fatty acid polyoxyethylene esters, sorbitan fatty acid esters (Span series) and their polyoxyethylene ethers (Tween series), phosphate esters (such as alkyl phosphate esters), silicone or fluorocarbon surfactants.

[0077] Specifically, thickeners include hydrogenated castor oil, polyamide wax, or organobentonite.

[0078] Specifically, stabilizers include antioxidants (such as butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), etc.).

[0079] The thick film paste composition provided in this application employs a lead-selenium-oxide system. Compared to tellurium oxide or silicon oxide, selenium oxide has advantages over lead-selenium oxide. , The chemical corrosion rate of passivation layer materials is moderate and controllable, but for ultrathin layers... The corrosiveness of the (tunneling oxide layer) is extremely weak. During the firing process, the glass powder softens and flows, preferentially reacting with the upper layer. The passivation layer reacts and etches itself open, forming a contact window. When the glass frit comes into contact with the underlying tunneling oxide layer, the corrosion reaction spontaneously stops or is greatly suppressed due to low chemical affinity and insufficient reactivity. This achieves "zero damage" or "low damage" to the tunneling oxide layer, improving photoelectric conversion efficiency.

[0080] This application also provides a method for preparing the aforementioned thick film paste composition, comprising the following steps:

[0081] Preparation of lead-selenium-based glass powder: Mix raw materials containing 30-90 wt% lead oxide and 10-70 wt% selenium oxide, melt at 450℃-650℃, then quench and pulverize to obtain glass powder.

[0082] Preparation of organic media: Mix polymer resin with organic solvent.

[0083] Mixing and dispersing: The conductive metal or its derivative, the lead-selenium glass powder and the organic medium are mixed and then rolled and dispersed evenly to obtain a thick film paste composition.

[0084] Specifically, according to the specified proportions, the required weights of oxides are added sequentially, mixed thoroughly, and then placed in a quartz crucible and dried at 105°C for one hour. The crucible is then melted in a muffle furnace with a set temperature range of 450°C-650°C and a time range of 20-40 minutes. The molten glass is poured into a cold rolling mill and cold-rolled and quenched to obtain glass slag. This slag is then pulverized using an air jet mill to obtain the desired glass powder particle size, ranging from 1.0 micrometers to 3.0 micrometers. Conductive metal powder, glass powder, organic carrier, and additives are added sequentially to a container according to the specified proportions, mixed thoroughly with a mixer, and then rolled uniformly using a three-roll mill before being dispensed.

[0085] The preparation method of the thick film paste composition provided in the above embodiments ensures that the final slurry can perfectly adapt to the multilayer film structure of the N-type battery by precisely controlling the melting temperature, quenching method and particle size of the glass powder, as well as the mixing process with the organic medium. The process is simple.

[0086] This application also provides a semiconductor electrode, which is formed on a semiconductor substrate by printing, drying and calcining the thick film paste composition described in any one of the claims.

[0087] Electrodes formed by the thick film paste composition of the present invention can achieve ideal contact in the multilayer film structure of N-type cells (especially TOPCon / BC) by "penetrating the passivation layer to contact polycrystalline silicon while protecting the tunneling oxide layer", thereby improving the photoelectric conversion efficiency of the cell by about 0.1%.

[0088] This application also provides a semiconductor article, comprising:

[0089] Semiconductor substrate;

[0090] One or more insulating films formed on at least one surface of the semiconductor substrate;

[0091] The semiconductor electrode formed on the one or more insulating films;

[0092] The electrode penetrates one or more insulating films to form an ohmic contact with the polycrystalline silicon layer located beneath the insulating films, and substantially does not penetrate the tunneling oxide layer located beneath the polycrystalline silicon layer.

[0093] It is understandable that, with the aid of lead-selenium glass, silver can precipitate from the molten glass during cooling and form a good ohmic contact on the polycrystalline silicon (poly-Si) surface through epitaxial growth or direct contact. Since the tunneling oxide layer remains intact, its excellent chemical passivation (reducing interface state density) and field-effect passivation (blocking minority carriers) functions are preserved. Recombination in the metal contact region is suppressed, directly increasing the cell's open-circuit voltage (Voc).

[0094] Furthermore, the semiconductor product is an N-type solar cell.

[0095] Furthermore, the N-type solar cell is a TOPCon cell or a BC cell.

[0096] This application also provides an application of the thick film paste composition described above in the manufacture of semiconductor products, characterized in that the composition is used to form a conductive electrode, which can form an ohmic contact with a polycrystalline silicon layer through one or more insulating films deposited on a semiconductor substrate, while maintaining a barrier to the tunneling oxide layer.

[0097] The thick film paste composition provided in this application is used in the manufacture of semiconductor products, employing a lead-selenium-oxide system. Compared to tellurium oxide or silicon oxide, selenium oxide has advantages in... , The chemical corrosion rate of passivation layer materials is moderate and controllable, but for ultrathin layers... The corrosiveness of the (tunneling oxide layer) is extremely low. During calcination, the glass powder softens and flows, preferentially reacting with and etching open the upper SiNx passivation layer to form contact windows. When the glass material comes into contact with the underlying tunneling oxide layer, the corrosion reaction spontaneously stops or is greatly inhibited due to low chemical affinity and insufficient reactivity. This achieves "zero damage" or "low damage" to the tunneling oxide layer, improving photoelectric conversion efficiency.

[0098] The beneficial effects of the present invention will be further illustrated below through specific embodiments and comparative examples. In all embodiments and comparative examples, the slurry preparation method described above is adopted, and the materials are added according to the formula in Table 1.

[0099] Example

[0100] Samples 1-6 were prepared according to the formulations (weight percentage, wt%) shown in Table 1 and the method described above.

[0101] Table 1 shows the composition comparison of the lead-selenium glass powder examples.

[0102]

[0103] Furthermore, the weight ratio of selenium oxide to lead oxide was calculated separately.

[0104]

[0105] The corresponding efficiencies of the prepared slurry batteries are as follows:

[0106]

[0107] Test subjects include 1 reference sample (BL, i.e., Baseline / Control Group) and 6 experimental samples (sample 1-sample 6).

[0108] Test parameters:

[0109] Eta (%): Photoelectric conversion efficiency (a core indicator, the higher the better).

[0110] Uoc (mV): Open-circuit voltage (reflects passivation effect and recombination level; the higher the better).

[0111] Isc (mA): Short-circuit current (reflects the ability to collect photogenerated carriers; the higher the better).

[0112] FF (%): Fill factor (reflects contact resistance and diode quality; the higher the better).

[0113] The efficiency of samples 1 and 3 reached 26.67%, which is 0.10% higher than the baseline sample (BL) of 26.57%. This directly verifies the aforementioned improvement of the photoelectric conversion efficiency of the battery by about 0.1%.

[0114] The Uoc of BL was 738.1 mV. Samples 1 (738.6 mV) and 3 (738.5 mV) both showed a slight increase of about 0.4-0.5 mV, while the remaining samples were the same as BL or fluctuated slightly. Open-circuit voltage is a key indicator for evaluating passivation effect and the integrity of the tunneling oxide layer. Uoc did not decrease, and even slightly increased, indicating that the lead-selenium glass powder of this invention did not damage the underlying tunneling oxide layer during sintering. The passivation structure of the battery was well protected, and minority carrier recombination did not increase.

[0115] Stability of short-circuit current (Isc). The Isc of all samples ranged from 18.710 to 18.717 mA, almost identical to BL (18.715 mA), with minimal fluctuation. The short-circuit current is primarily affected by optical design (anti-reflection) and collection efficiency. The stability of Isc indicates that the printing pattern accuracy and light-shielding area of ​​the paste have not deteriorated. The electrodes effectively collect charge carriers, and there is no current loss due to contact issues.

[0116] The fill factor is the most sensitive indicator of contact resistance and series resistance. Samples 1 and 3 showed a significant improvement in fill factor (FF) of 0.27-0.28 percentage points (absolute value), which is highly remarkable. This indicates that an excellent ohmic contact has been formed between the electrode and the polysilicon layer (poly-Si). The contact resistance (Rc) is significantly reduced, which is a direct reflection of the lead-selenium glass powder's ability to "pass through the insulating film" and make good contact with the underlying polysilicon.

[0117] Therefore, the electrode prepared by applying the thick film paste composition described in this invention achieves a significant increase in fill factor (FF) (+0.27% abs) in N-type cells, and at the same time, under the premise of keeping the open circuit voltage (Uoc) stable, it ultimately promotes an increase in absolute photoelectric conversion efficiency (Eta) of 0.1%.

[0118] Furthermore, the table below presents a comparison of accelerated aging test (corrosion resistance test in acetic acid environment) results.

[0119]

[0120] Test conditions: 3% (v / v) mixed aqueous solution of acetic acid and saturated potassium chloride, 85±2℃ (constant temperature test chamber).

[0121] Acetic acid environment: During the encapsulation process of photovoltaic modules, the encapsulation materials (such as EVA, ethylene-vinyl acetate copolymer) decompose and release small amounts of acetic acid under long-term humid and hot conditions. Acetic acid corrodes the silver grid electrodes, leading to power degradation of the module. Therefore, acetic acid testing is an important indicator for evaluating the corrosion resistance and long-term reliability of the electrodes.

[0122] Saturated potassium chloride: Provides a stable ionic environment, simulating the humid and saline conditions in actual use.

[0123] 85℃ high temperature: Accelerates the aging reaction and quickly assesses the weather resistance of materials.

[0124] Table values: The data in the table (BL 32%, Sample 1 20%, etc.) represent the degradation rate or failure rate after aging (the lower the value, the better the corrosion resistance and the higher the reliability).

[0125] As shown above, the test results of all experimental samples (samples 1-6) are significantly better than those of the baseline sample (BL). The attenuation rate of BL is as high as 32%, while the attenuation rate of the experimental samples is between 12% and 21%, which is much lower than that of the control group. Among them, sample 5 performed the best, with an attenuation rate of only 12%, which is 20 percentage points lower than that of BL; samples 2, 3, and 6 also performed well, with attenuation rates controlled between 15% and 18%.

[0126] It is understood that the thick-film paste composition provided in this embodiment, using lead-selenium-based glass powder, forms a glass layer after sintering, exhibiting excellent chemical inertness, especially in acidic environments. The introduction of selenium oxide may alter the glass network structure, making it denser and more resistant to corrosive media such as acetic acid. The residual glass phase after sintering not only acts as an adhesion agent but also forms a protective film around the silver particles, preventing acetic acid from penetrating into the silver electrode and thus slowing down the silver corrosion rate.

[0127] It is understood that the thick film paste composition provided in this embodiment has a dense electrode microstructure. Thanks to the suitable melting characteristics and viscosity of lead-selenium glass (melting temperature 450℃-650℃), a dense electrode film layer with low porosity is formed during the sintering process. The dense structure reduces the channels for corrosive liquids (acetic acid solution) to penetrate along grain boundaries or pores, fundamentally improving the corrosion resistance of the electrode.

[0128] It is understood that the thick-film paste composition provided in this embodiment has an intact interface, with the lead-selenium glass "virtually not penetrating the tunneling oxide layer," avoiding the direct formation of alloying peaks between silver and the silicon substrate. Such a sharp interface structure is often a weak point that accelerates corrosion. The flat, complete interface structure further improves the overall aging resistance.

[0129] The thick-film paste composition provided in this embodiment not only improves efficiency but also significantly enhances the corrosion resistance and long-term reliability of the electrodes. In the photovoltaic industry, the long-term reliability of modules is as important as initial efficiency. The significant improvement in acetic acid testing translates to a longer module lifespan: cells made using the paste of this invention are better able to resist corrosion caused by the aging of encapsulation materials during long-term outdoor operation, delaying power degradation; higher power generation yield and a lower degradation rate mean higher total power generation over the entire module's lifespan. Wider application scenarios are also possible, as its excellent corrosion resistance allows the cell to better adapt to harsh environments such as humid and hot regions or coastal areas.

[0130] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A thick-film paste composition, characterized in that, Include: a) A conductive metal or its derivative, comprising 75-95 wt% based on the total solids in the composition; b) Lead-selenium glass powder, on a solids basis, comprising 0.5-15 wt%; wherein the lead-selenium glass powder comprises 30-90 wt% lead oxide and 10-70 wt% selenium oxide; and c) Organic media.

2. The thick film paste composition according to claim 1, characterized in that, The conductive metal includes silver.

3. The thick film paste composition according to claim 1, characterized in that, The content of the conductive metal or its derivative is 90-95 wt% of the total solid content.

4. The thick film paste composition according to claim 1, characterized in that, The softening point temperature of the lead-selenium glass powder is related to its melting temperature, which allows it to etch through the insulating film during the calcination process, but not through the tunneling oxide layer.

5. The thick film paste composition according to claim 1, characterized in that, The particle size range of the lead-selenium glass powder is 1.0 micrometer to 3.0 micrometer.

6. The thick film paste composition according to claim 1, characterized in that, The melting temperature of the lead-selenium glass powder is 450℃-650℃.

7. The thick film paste composition according to claim 1, characterized in that, The composition further comprises one or more additives selected from the group consisting of: .

8. The thick film paste composition according to claim 1, characterized in that, The organic medium includes polymer resins and organic solvents.

9. The thick film paste composition according to claim 8, characterized in that, The organic medium also includes one or more additives selected from the group consisting of stabilizers, surfactants, and thickeners.

10. A method for preparing a thick-film paste composition as described in any one of claims 1-9, characterized in that, Includes the following steps: Preparation of lead-selenium-based glass powder: Mix raw materials containing 30-90 wt% lead oxide and 10-70 wt% selenium oxide, melt at 450℃-650℃, then quench and pulverize to obtain glass powder; Preparation of organic media: Mixing polymer resin with organic solvent; Mixing and dispersing: The conductive metal or its derivative, the lead-selenium glass powder and the organic medium are mixed and then rolled and dispersed evenly to obtain a thick film paste composition.

11. A semiconductor electrode, characterized in that, The semiconductor electrode is formed on a semiconductor substrate by printing, drying and calcining the thick film paste composition of any one of claims 1-9.

12. A semiconductor article, characterized in that, include: Semiconductor substrate; One or more insulating films formed on at least one surface of the semiconductor substrate; The semiconductor electrode as described in claim 10 is formed on the one or more insulating films; The electrode penetrates one or more insulating films to form an ohmic contact with the polycrystalline silicon layer located beneath the insulating films, and substantially does not penetrate the tunneling oxide layer located beneath the polycrystalline silicon layer.

13. The semiconductor article according to claim 12, characterized in that, The semiconductor product is an N-type solar cell.

14. The semiconductor article according to claim 13, characterized in that, The N-type solar cell is either a TOPCon cell or a BC cell.

15. The use of a thick film paste composition as described in any one of claims 1-9 in the manufacture of semiconductor articles, characterized in that, The composition is used to form a conductive electrode that can form an ohmic contact with a polycrystalline silicon layer through one or more insulating films deposited on a semiconductor substrate, while maintaining a barrier to the tunneling oxide layer.

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