Glass powder composition and conductive paste comprising same

Abstract

The present invention relates to a glass powder composition, which comprises: a) a first glass powder and b) a second glass powder. The first glass powder comprises 30-50 mol% of TeO2, 15-35 mol% of Li2O, 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O, more than 0 mol% and less than 5 mol% of at least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2 and BaO, 0-25 mol% of PbO, 0-10 mol% of B2O3 and 0-10 mol% of a fluorine-containing compound, wherein the molar percentages are based on the total number of moles of all compounds in the first glass powder. The second glass powder comprises 10-35 mol% of SiO2, 15-35 mol% of PbO, 5-30 mol% of at least one oxide selected from Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3, Cu2O and B2O3, 0-40 mol% of TeO2, and 0-15 mol% of Li2O, wherein the mole percentages are based on the total number of moles of all compounds in the second glass powder. The present invention also relates to a conductive paste comprising the glass powder composition.

Description

Glass powder composition and conductive paste comprising said glass powder composition Technical Field

[0001] This invention relates to a glass powder composition and a conductive paste comprising the glass powder composition. Background Technology

[0002] Solar energy is an attractive green energy source because it is sustainable and produces only non-polluting byproducts. Therefore, solar cells, which utilize the photovoltaic effect to convert solar energy into electricity, have been developed. Solar cells are typically made of semiconducting materials, such as appropriately doped silicon. When light shines on a solar cell, some of the incident light is reflected by the surface, while the remaining light is transmitted into the cell. The transmitted photons are absorbed by the solar cell, which in turn excites electrons in the semiconducting material to create electron-hole pairs. These electrons and holes are guided through electrodes on the front side (the side exposed to light) and the back side (the side not exposed to light), respectively, to form a current, thus generating electrical energy.

[0003] Electrodes in solar cells that contact the silicon wafer are typically manufactured by screen printing a conductive paste onto a substrate, followed by sintering the paste. The conductive paste contains glass powder, conductive powder, and an organic carrier. During the sintering process, the glass powder erodes the passivation layer, allowing the conductive powder in the paste to form contact with the silicon wafer beneath the passivation layer after sintering.

[0004] However, in the existing technology, when glass powder erodes the passivation layer, the contact time in different microscopic areas is different, which makes it impossible to form uniform erosion. This results in insufficient or excessive erosion in some areas, thus failing to improve the efficiency of solar cells.

[0005] Therefore, there is an urgent need in the field for a glass powder that can uniformly erode the passivation layer, thereby improving the efficiency of solar cells. Summary of the Invention

[0006] Therefore, the present invention provides a glass powder composition comprising:

[0007] a) First glass powder, and

[0008] b) Second glass powder,

[0009] The first glass powder contains:

[0010] 30-50 mol% TeO2,

[0011] 15-35 mol% Li₂O,

[0012] 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O,

[0013] At least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2, and BaO, greater than 0 and less than 5 mol%.

[0014] 0-25 mol% PbO,

[0015] 0-10 mol% of B2O3, and

[0016] 0-10 mol% of fluorine-containing compounds,

[0017] The molar percentages mentioned therein are based on the total number of moles of all compounds in the first glass powder;

[0018] The second glass powder contains:

[0019] 10-35 mol% SiO2,

[0020] 15-35 mol% PbO,

[0021] 5-30 mol% of at least one oxide selected from Bi₂O₃, Na₂O, K₂O, SrO, CaO, ZnO, MoO₃, WO₃, Cu₂O, and B₂O₃.

[0022] 0-40 mol% TeO2, and

[0023] 0-15 mol% Li₂O,

[0024] The molar percentages mentioned therein are based on the total number of moles of all compounds in the second glass powder.

[0025] The present invention also provides a conductive paste comprising the above-described glass powder composition.

[0026] The present invention also provides an electrode for a crystalline silicon solar cell, which is formed by sintering the conductive paste.

[0027] The present invention also provides a crystalline silicon solar cell, comprising a substrate and the electrodes bonded to the substrate.

[0028] The applicant has discovered that solar cells prepared using conductive pastes containing the glass powder composition of the present invention have improved solar cell efficiency. Attached Figure Description

[0029] Figure 1a shows the surface morphology of the metallized region of the comparison sample 2 after the silver grid lines were removed.

[0030] Figure 1b is a cross-sectional view of the metallized region of the comparative sample 2.

[0031] Figure 2a is a surface morphology diagram of the metallized region of sample 1 of the present invention after the silver grid lines are removed.

[0032] Figure 2b is an enlarged image of Figure 2a. Detailed Implementation

[0033] conductive paste

[0034] According to the present invention, a solid electrode is formed by applying a conductive paste to the surface of a solar cell wafer and forming an electrical contact with the surface during sintering. According to the present invention, the conductive paste comprises:

[0035] a) 80-93% by weight of silver powder,

[0036] b) 1-10% by weight of a glass powder composition, and

[0037] c) 5-18% by weight of organic carrier,

[0038] The weight percentage is based on the total weight of the conductive paste.

[0039] a) Silver powder

[0040] The silver powder present in the conductive paste provides metallic conductivity to the solid electrode formed during the sintering of the conductive paste.

[0041] According to the present invention, the silver powder (silver particles) can have various shapes, surfaces, sizes, and surface area to volume ratios. Many shapes are known to those skilled in the art. Some examples are spherical, angular, elongated (rod-like or needle-like), and flat (sheet-like). Silver powder can also exist as a combination of particles of different shapes. According to the present invention, silver powder having a shape or combination of shapes that is beneficial to the sintering, electrical contact, adhesion, and conductivity of the resulting electrode is preferred. Without considering surface characteristics, one way to characterize such shapes is by means of the parameters length, width, and thickness. For the purposes of the present invention, the length of the particle is given by the length of the longest spatial displacement vector whose two endpoints are contained within the particle. The width of the particle is given by the length of the longest spatial displacement vector perpendicular to the length vector defined above and whose two endpoints are contained within the particle. The thickness of the particle is given by the length of the longest spatial displacement vector perpendicular to both the length vector and the width vector defined above and whose two endpoints are contained within the particle. In one embodiment of the invention, the silver powder preferably has the most uniform shape possible, i.e., a shape in which the ratios of length, width, and thickness are as close as possible to 1, preferably all ratios are in the range of 0.7-1.5, more preferably 0.8-1.3. In one embodiment of the invention, preferred examples of the shape of the silver powder are spherical and cubic or combinations thereof, or one or more of them combined with other shapes. In one embodiment of the invention, the silver powder in the conductive paste is spherical.

[0042] Particle size D50 is a particle characteristic known to those skilled in the art. The determination of particle size D50 is also known to those skilled in the art. According to the present invention, the particle size D50 of the silver powder is preferably 0.5-10 μm, more preferably 0.5-3 μm.

[0043] In one embodiment of the invention, the silver powder is present in a proportion of greater than or equal to 80% by weight of the conductive paste, for example, greater than or equal to 85% by weight or greater than or equal to 90% by weight.

[0044] In a preferred embodiment of the invention, the silver powder is present in a proportion of 80-93% by weight of the conductive paste, for example, 85-90% by weight.

[0045] b) Glass powder composition

[0046] According to the present invention, the conductive paste contains glass powder to cause etching. According to the present invention, the glass powder used is a glass powder composition comprising:

[0047] a) First glass powder, and

[0048] b) Second glass powder,

[0049] The first glass powder contains:

[0050] 30-50 mol% TeO2,

[0051] 15-35 mol% Li₂O,

[0052] 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O,

[0053] At least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2, and BaO, greater than 0 and less than 5 mol%.

[0054] 0-25 mol% PbO,

[0055] 0-10 mol% of B2O3, and

[0056] 0-10 mol% of fluorine-containing compounds,

[0057] The molar percentages mentioned therein are based on the total number of moles of all compounds in the first glass powder;

[0058] The second glass powder contains:

[0059] 10-35 mol% SiO2,

[0060] 15-35 mol% PbO,

[0061] 5-30 mol% of at least one oxide selected from Bi₂O₃, Na₂O, K₂O, SrO, CaO, ZnO, MoO₃, WO₃, Cu₂O, and B₂O₃.

[0062] 0-40 mol% TeO2, and

[0063] 0-15 mol% Li₂O,

[0064] The molar percentages mentioned therein are based on the total number of moles of all compounds in the second glass powder.

[0065] In a preferred embodiment, the first glass powder contains 35-45 mol% TeO2.

[0066] In a preferred embodiment, the first glass powder contains 15-30 mol% Li2O.

[0067] In a preferred embodiment, the first glass powder comprises 5-25 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O.

[0068] In a preferred embodiment, the first glass powder contains 0.5-4 mol%, for example 1-3 mol%, of at least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2 and BaO.

[0069] In a preferred embodiment, the first glass powder may contain 10-25 mol% PbO.

[0070] In a preferred embodiment, the first glass powder may contain 0.5-3 mol% B2O3.

[0071] In a preferred embodiment, the first glass powder may contain 10-25 mol% PbO and 0.5-3 mol% B2O3.

[0072] In a preferred embodiment, the first glass powder may contain 1-10 mol%, for example, 1-5 mol%, of a fluorinated compound. The fluorinated compound may include PbF2, NaF, LiF, KF, CaF2, ZnF2, NaBF4, LiBF4, YF3, YOF, and combinations thereof, preferably PbF2, NaF, LiF, KF, and CaF2, and more preferably PbF2 and NaF.

[0073] In a preferred embodiment, the second glass powder contains 10-30 mol% SiO2.

[0074] In a preferred embodiment, the second glass powder contains 15-30 mol% PbO.

[0075] In a preferred embodiment, the second glass powder comprises 5-25 mol% of at least one oxide selected from Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3, Cu2O and B2O3.

[0076] In a preferred embodiment, the second glass powder may contain 20-40 mol% TeO2.

[0077] In a preferred embodiment, the second glass powder may contain 5-15 mol% Li2O.

[0078] In a preferred embodiment, the second glass powder may contain 20-40 mol% TeO2 and 5-15 mol% Li2O.

[0079] In a preferred embodiment, the glass powder composition comprises:

[0080] a) First glass powder, and

[0081] b) Second glass powder,

[0082] The first glass powder contains:

[0083] 35-45 mol% TeO2,

[0084] 20-30 mol% Li₂O,

[0085] 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O,

[0086] 1-4 mol% of at least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2, and BaO,

[0087] 10-25 mol% PbO,

[0088] 1-5 mol% of B2O3, and

[0089] 1-5 mol% of fluorine-containing compounds,

[0090] The molar percentages mentioned therein are based on the total number of moles of all compounds in the first glass powder;

[0091] The second glass powder contains:

[0092] 10-30 mol% SiO2,

[0093] 15-30 mol% PbO,

[0094] 10-25 mol% of at least one oxide selected from Bi₂O₃, Na₂O, K₂O, SrO, CaO, ZnO, MoO₃, WO₃, Cu₂O, and B₂O₃.

[0095] 20-40 mol% TeO2, and

[0096] 5-15 mol% Li₂O,

[0097] The molar percentages mentioned therein are based on the total number of moles of all compounds in the second glass powder.

[0098] According to the present invention, the glass powder preferably has a glass transition temperature Tg lower than the desired sintering temperature of the conductive paste. In one embodiment of the invention, the first glass powder preferably has a glass transition temperature Tg of 200-400°C, for example, 300-400°C. In one embodiment of the invention, the second glass powder preferably has a glass transition temperature Tg of 300-500°C, for example, 350-450°C or 400-450°C. The glass transition temperature Tg is the temperature at which a rigid solid transforms into a partially flowing supercooled melt upon heating. Methods for determining the glass transition temperature Tg are well known to those skilled in the art. Etching and sintering caused by the glass powder occur at a temperature higher than the glass transition temperature Tg of the glass powder, and preferably this glass transition temperature Tg is lower than the desired peak sintering temperature.

[0099] According to the present invention, glass powder particles can have various shapes, surface properties, sizes, and surface area to volume ratios. Many shapes of glass powder particles are known to those skilled in the art. Some examples are spherical, angular, elongated (rod-like or needle-like), and flat (plate-like). Glass powder particles can also exist as combinations of particles of different shapes. According to the present invention, glass powder having a shape or combination of shapes that is beneficial to the sintering, adhesion, electrical contact, and conductivity of the resulting electrode is preferred.

[0100] According to the present invention, the first glass powder and the second glass powder each independently have a particle size D50 of 0.1-10 μm, preferably 0.2-7.0 μm, and more preferably 0.6-2.5 μm. The determination of particle size D50 is well known to those skilled in the art.

[0101] In one embodiment of the invention, the glass powder composition is present in a proportion of 1-10% by weight of the conductive paste, preferably 1-8% by weight, more preferably 1-5% by weight.

[0102] In one embodiment of the present invention, the first glass powder of the present invention can be prepared by the following method: combining all the components of the first glass powder together and melting them to obtain a glass frit, cold rolling or water quenching the glass frit to obtain glass slag, and then wet grinding or dry grinding the glass slag and classifying it to obtain the first glass powder with the desired particle size.

[0103] In one embodiment of the present invention, the second glass powder of the present invention can be prepared by the following method: combining all the components of the second glass powder together and melting them to obtain a glass frit, cold rolling or water quenching the glass frit to obtain glass slag, and then wet grinding and / or dry grinding the glass slag and classifying it to obtain the second glass powder of the desired particle size.

[0104] Preferably, the "melting" is carried out by loading the components of the glass powder into a crucible, placing the crucible in a muffle furnace, and melting it at a high temperature; the "cold rolling" is carried out by cold rolling the glass molten block in a cold rolling mill; the "water quenching" is carried out by removing the glass molten block from the muffle furnace and pouring it into a bucket containing deionized water; the "wet grinding and / or dry grinding and grading of the glass slag" is carried out, for example, by grinding the glass slag into coarse powder using a ball mill, and then grinding and grading the coarse powder using an air jet mill.

[0105] In the above methods, the temperature of the muffle furnace is high enough for the components of the molten glass powder, and the melting time is long enough for the components to be mixed evenly.

[0106] More preferably, in the preparation of glass powder, the temperature of the muffle furnace is 900-1200℃ and the melting time is 15 to 60 minutes.

[0107] In one embodiment of the present invention, the glass powder composition of the present invention is prepared by mixing a first glass powder and a second glass powder.

[0108] In one embodiment of the invention, the ratio of the first glass powder to the second glass powder in the glass powder composition is 7:1 to 1:3 by weight, preferably 4:1 to 1:1.

[0109] c) Organic carrier

[0110] In one embodiment of the invention, the conductive paste comprises an organic carrier commonly used in the art. Preferred organic carriers are those that provide optimal stability to the components within the conductive paste and impart tackiness to the conductive paste, allowing for effective printability.

[0111] In one embodiment, the amount of organic carrier may be 5-18% by weight, for example 7-15% by weight or 8-12% by weight, based on the total weight of the conductive paste.

[0112] In one embodiment, the organic carrier includes a solvent, a binder (e.g., an organic binder such as a polymer or resin), a surfactant, an additive, or any combination thereof, preferably an organic binder and a solvent. The additive includes film-forming aids (e.g., dodecyl alcohol esters), thixotropic agents, viscosity modifiers, stabilizers, thickeners, emulsifiers, dispersants, slip agents (e.g., dimethyl silicone oil), or pH adjusters, or any combination thereof. For example, in one embodiment, the organic carrier includes one or more binders in an organic solvent.

[0113] The adhesive may be present in an amount of 5-50% by weight, for example 10-45% by weight or 20-40% by weight, based on the total weight of the organic carrier. Preferred adhesives are those that promote the formation of conductive pastes with favorable stability, printability, tackiness, and sintering properties. Preferred adhesives (which generally fall within the category referred to as "resins") are polymeric adhesives, monomeric adhesives, and adhesives that are combinations of polymers and monomers. Polymeric adhesives may also be copolymers.

[0114] Preferred polymeric adhesives include adhesives carrying functional groups in the polymer backbone, adhesives carrying functional groups outside the backbone, and adhesives carrying functional groups both inside and outside the backbone. Preferred polymers carrying functional groups in the backbone include, for example, polyesters, substituted polyesters, polycarbonates, substituted polycarbonates, polymers carrying cyclic groups in the backbone, polysaccharides, substituted polysaccharides, polyurethanes, substituted polyurethanes, polyamides, substituted polyamides, phenolic resins, substituted phenolic resins, copolymers of one or more monomers of the above polymers (optionally with other comonomers), or combinations of at least two of the above.

[0115] Preferred polymers carrying cyclic groups in the main chain include, for example, polyvinyl butyral (PVB) and its derivatives, as well as polyterpineol and its derivatives, or mixtures thereof. Preferred polysaccharides include, for example, cellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, propylcellulose, hydroxypropylcellulose, butylcellulose, its derivatives, and mixtures of at least two thereof. Other preferred polymers include, for example, cellulose ester resins, such as cellulose acetate propionate, cellulose acetate butyrate, and any combination thereof. Other preferred polymers are those disclosed in U.S. Patent Application Publication No. 2013 / 0180583, which is incorporated herein by reference.

[0116] Preferred polymers carrying functional groups outside the polymer backbone are polymers carrying amide groups, polymers carrying acid and / or ester groups (commonly referred to as acrylic resins), or polymers carrying combinations of the above functional groups, or combinations thereof. Preferred polymers carrying amide groups outside the backbone include, for example, polyvinylpyrrolidone (PVP) and its derivatives. Preferred polymers carrying acid and / or ester groups outside the backbone include, for example, polyacrylic acid and its derivatives, polymethyl methacrylate (PMMA) and its derivatives, or mixtures thereof.

[0117] Preferred monomeric adhesives include, for example, ethylene glycol-based monomeric adhesives. Preferred ethylene glycol-based monomeric adhesives are adhesives having multiple ether groups, multiple ester groups, or having one ether group and one ester group. Preferred ether groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, and higher alkyl ethers. Preferred ester groups are acetates and their alkyl ether derivatives, preferably ethylene glycol monobutyl ether monoacetate or mixtures thereof.

[0118] Preferred adhesives in this invention are, for example, alkyl cellulose (preferably ethyl cellulose), its derivatives, and mixtures thereof with other adhesives listed above.

[0119] The amount of organic solvent can be 40-90% by weight, more preferably 35-85% by weight, based on the total weight of the organic carrier.

[0120] Preferred solvents are those that allow the formation of conductive pastes with favorable viscosity, printability, stability, and sintering properties. All solvents known in the art and considered suitable for use in this invention can be used as solvents in organic carriers. According to the invention, preferred solvents are those that allow for a preferred high level of printability of the conductive paste as described above. Preferred solvents according to the invention are those present in liquid form at standard ambient temperature and pressure (SATP) (25°C, 100 kPa).

[0121] Preferred solvents are polar or nonpolar, protonated or proton-inert, aromatic or non-aromatic. Preferred solvents include, for example, monools, diols, polyols, monoesters, diesters, polyesters, monoethers, diethers, polyethers, solvents including at least one or more of these functional groups, optionally including other functional groups, and mixtures of two or more of the above solvents, such as diethylene glycol butyl ether acetate.

[0122] The organic carrier may also include a surfactant. The amount of surfactant may be 0-10% by weight, preferably 0-8% by weight, more preferably 0.01-6% by weight, based on the total weight of the organic carrier. Preferred surfactants in this invention are those that promote the formation of conductive pastes with favorable stability, printability, viscosity, and sintering properties. All surfactants known in the art and considered suitable in this invention may be used as surfactants in the organic carrier. Preferred surfactants may have nonionic, anionic, cationic, amphoteric, or zwitterionic heads. Preferred surfactants are polymeric and monomeric, or mixtures thereof.

[0123] According to the present invention, the conductive paste optionally contains additives commonly used in the art. The amount of the additive can be 1-15% by weight, preferably 5-10% by weight, based on the total weight of the organic carrier. Preferred conductive paste additives are components added to the conductive paste in addition to the components already explicitly mentioned, which are used to promote higher performance of the conductive paste, the electrodes made therefrom, or the resulting crystalline silicon solar cells. All additives known in the art and considered suitable in this invention can be used as conductive paste additives. Preferred additives are film-forming aids, thixotropic agents, viscosity modifiers, stabilizers, thickeners, emulsifiers, dispersants, slip agents, or pH adjusters, and any combination thereof. Preferred thixotropic agents herein are carboxylic acid derivatives, preferably fatty acid derivatives, or combinations thereof. Preferred fatty acid derivatives are C9H 19 COOH (decanoic acid), C 11 H 23 COOH (lauric acid), C 13 H 27 COOH (myristic acid), C 15 H 31 COOH (palmitic acid), C 17 H 35 COOH (stearic acid), C 18 H 34 O2 (oleic acid), C 18 H 32 O2 (linoleic acid), castor oil, hydrogenated castor oil, or combinations thereof. The preferred film-forming aid described herein is dodecyl alcohol ester. The preferred slip agent described herein is dimethyl silicone oil.

[0124] In one embodiment of the invention, to form a conductive paste, glass powder, silver powder, an organic carrier, and optional conductive paste additives can be combined using any method known in the art for preparing pastes. The details of the preparation method are not critical, as long as it produces a homogeneously dispersed paste. The components can be mixed, for example, using a mixer, and then passed through, for example, a three-roll mill to produce a uniformly dispersed paste.

[0125] In one embodiment of the invention, in order to form a conductive paste, the first glass powder and the second glass powder may be premixed and then mixed with silver powder, an organic carrier, and optional conductive paste additives.

[0126] In one embodiment of the invention, in order to form a conductive paste, a first glass powder, a second glass powder, silver powder, an organic carrier, and optional conductive paste additives are directly mixed.

[0127] Electrodes used in crystalline silicon solar cells

[0128] The electrode for crystalline silicon solar cells described in this invention is formed from the aforementioned conductive paste through a sintering process. The sintering process is performed according to conventional methods well known to those skilled in the art.

[0129] In one embodiment of the present invention, the sintering temperature of the conductive paste is 700-850°C, preferably 700-800°C.

[0130] Crystalline silicon solar cells

[0131] The present invention also relates to a crystalline silicon solar cell, comprising a substrate and the electrodes bonded to the substrate.

[0132] In one embodiment of the present invention, the crystalline silicon solar cell includes a PERC solar cell, a BC solar cell, and a TOPCon solar cell.

[0133] In one embodiment of the invention, the preferred crystalline silicon solar cell according to the invention is a crystalline silicon solar cell with high efficiency in the ratio of total energy of incident light to electrical energy output. Lightweight and durable crystalline silicon solar cells are also preferred. The crystalline silicon solar cell may also include an additional layer for chemical / mechanical protection.

[0134] In one embodiment of the present invention, the crystalline silicon solar cell substrate of the present invention is a substrate for crystalline silicon solar cells known to those skilled in the art.

[0135] The crystalline silicon solar cell of the present invention has electrodes bonded to the substrate, formed by sintering the conductive paste of the present invention.

[0136] In one embodiment of the invention, the conductive paste of the invention is applied to a substrate, such as a semiconductor substrate (e.g., a crystalline silicon wafer), to form a printed electrode.

[0137] The conductive paste of the present invention can be applied to a substrate by any method known in the art and considered applicable in this invention. Examples of such methods include, but are not limited to, dipping, impregnation, casting, dropping, injection, spraying, doctor blade coating, curtain coating, brush coating, or printing, or combinations of at least two thereof. Preferred printing techniques are inkjet printing, screen printing, flexographic printing, offset printing, letterpress printing, or stencil printing, or combinations of at least two thereof. According to the present invention, the conductive paste of the present invention is preferably applied by printing, and more preferably by screen printing.

[0138] The printed electrodes need to be sintered to form a solid conductor. Firing is well known in the art and can be considered appropriate in any manner for implementation in this invention. Preferably, sintering is performed at a Tg higher than that of the glass powder material.

[0139] Outside the area occupied by the electrodes, the substrate of the present invention, preferably a crystalline silicon wafer, has a region in which light can be absorbed efficiently to generate electron-hole pairs and to be separated from holes and electrons by efficiently crossing boundaries, preferably across pn junction boundaries.

[0140] The pn junction boundary is located at the junction of the front and back doped layers of the wafer. In an N-type solar cell, the back doped layer is doped with an n-type dopant and the front doped layer is doped with a p-type dopant. In a P-type solar cell, the back doped layer is doped with a p-type dopant and the front doped layer is doped with an n-type dopant. According to a preferred embodiment of the invention, a wafer with a pn junction boundary is fabricated by first providing a doped silicon substrate and then applying a doped layer of the opposite type to one side of the substrate.

[0141] The aforementioned dopants are preferably dopants that form pn junction boundaries by introducing electrons or holes into the band structure when added to a crystalline silicon wafer. According to the invention, it is preferred to specifically select the type and concentration of these dopants to adjust the band structure profile of the pn junction and to set the light absorption and conductivity profiles as needed. A preferred p-type dopant according to the invention is a dopant that adds holes to the band structure of the crystalline silicon wafer. All dopants known in the art and considered suitable for use in this invention can be used as p-type dopants. A preferred p-type dopant according to the invention is a trivalent element, particularly a trivalent element of group 13 in the periodic table. Preferred group 13 elements in the periodic table herein include, but are not limited to, boron, aluminum, gallium, indium, thallium, or combinations of at least two of them, with boron being particularly preferred.

[0142] The preferred n-type dopant according to the invention is a dopant that adds electrons to the band structure of a crystalline silicon wafer. All dopants known in the art and considered applicable in this invention can be used as n-type dopants. The preferred n-type dopant according to the invention is an element of Group 5 of the periodic table. Preferred Group 5 elements herein include nitrogen, phosphorus, arsenic, antimony, bismuth, or combinations of at least two thereof, with phosphorus being particularly preferred.

[0143] In one embodiment of the invention, a passivation layer may be applied to a substrate, preferably the front and / or back sides of a crystalline silicon wafer as an outer layer. Preferably, the passivation layer is one that reduces the electron / hole recombination rate near the electrode interface. Any passivation layer known in the art and considered suitable for use in this invention may be used. According to the invention, the passivation layer may be silicon nitride, aluminum oxide, silicon dioxide, and titanium dioxide. According to a preferred embodiment, aluminum oxide is used as the passivation layer.

[0144] In one embodiment of the present invention, in addition to the aforementioned layers that directly promote the main functions of the crystalline silicon solar cell, other layers may be added for mechanical and chemical protection.

[0145] The battery can be encapsulated to provide chemical protection. Encapsulation is well known in the art and any encapsulation suitable for this invention can be employed. According to a preferred embodiment, a transparent polymer (commonly referred to as a transparent thermoplastic resin) is used as the encapsulation material, provided that such an encapsulation exists. Preferred transparent polymers herein are silicone rubber and polyethylene vinyl acetate (EVA).

[0146] A transparent glass sheet can also be added to the front side of a crystalline silicon solar cell to provide it with mechanical protection. Transparent glass sheets are well known in the art, and any transparent glass sheet applicable in this invention can be used.

[0147] A back-side protective material can be added to the back of a crystalline silicon solar cell to provide mechanical protection. Back-side protective materials are well known in the art, and any back-side protective material considered applicable in this invention can be used. A preferred back-side protective material according to the invention is one with good mechanical properties and weather resistance. A preferred back-side protective material according to the invention is polyethylene terephthalate having a polyvinyl fluoride layer (e.g., a PTFE layer). Preferably, according to the invention, the back-side protective material is present below the encapsulation layer (in the presence of both a back-side protective layer and encapsulation).

[0148] Frame materials can be added to the outside of crystalline silicon solar cells to provide mechanical support. Frame materials are well known in the art, and any frame material considered applicable in this invention can be used. A preferred frame structure according to the invention is aluminum.

[0149] Those skilled in the art will be able to more readily understand the present invention based on the following embodiments:

[0150] Implementation Scheme 1. A glass powder composition comprising:

[0151] a) First glass powder, and

[0152] b) Second glass powder,

[0153] The first glass powder contains:

[0154] 30-50 mol% TeO2,

[0155] 15-35 mol% Li₂O,

[0156] 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O,

[0157] At least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2, and BaO, greater than 0 and less than 5 mol%.

[0158] 0-25 mol% PbO,

[0159] 0-10 mol% of B2O3, and

[0160] 0-10 mol% of fluorine-containing compounds,

[0161] The molar percentages mentioned therein are based on the total number of moles of all compounds in the first glass powder;

[0162] The second glass powder contains:

[0163] 10-35 mol% SiO2,

[0164] 15-35 mol% PbO,

[0165] 5-30 mol% of at least one oxide selected from Bi₂O₃, Na₂O, K₂O, SrO, CaO, ZnO, MoO₃, WO₃, Cu₂O, and B₂O₃.

[0166] 0-40 mol% TeO2, and

[0167] 0-15 mol% Li₂O,

[0168] The molar percentages mentioned therein are based on the total number of moles of all compounds in the second glass powder.

[0169] Implementation Scheme 2. The glass powder composition according to Implementation Scheme 1, wherein the first glass powder comprises 10-25 mol% PbO and 0.5-3 mol% B2O3.

[0170] Implementation Scheme 3. The glass powder composition according to Implementation Scheme 1 or 2, wherein the fluorine-containing compound includes PbF2, NaF, LiF, KF, CaF2, ZnF2, NaBF4, LiBF4, YF3, YOF and combinations thereof, preferably PbF2, NaF, LiF, KF, and CaF2, and more preferably PbF2 and NaF.

[0171] Implementation Scheme 4. The glass powder composition according to any one of Implementation Schemes 1-3, wherein the second glass powder comprises 20-40 mol% TeO2 and 5-15 mol% Li2O.

[0172] Implementation Scheme 5. The glass powder composition according to any one of Implementation Schemes 1-4, wherein the first glass powder and the second glass powder each independently have a particle size D50 of 0.1-10 μm, preferably 0.2-7.0 μm, more preferably 0.6-2.5 μm.

[0173] Implementation Scheme 6. The glass powder composition according to any one of Implementation Schemes 1-5, wherein the ratio of the first glass powder to the second glass powder in the glass powder composition is from 7:1 to 1:3 by weight.

[0174] Implementation Scheme 7. A conductive paste comprising:

[0175] a) Silver powder,

[0176] b) The glass powder composition according to any one of embodiments 1-6, and

[0177] c) Organic carrier.

[0178] Implementation Scheme 8. The conductive paste according to Implementation Scheme 7, wherein the conductive paste comprises:

[0179] a) 80-93% by weight of silver powder,

[0180] b) 1-10% by weight of a glass powder composition, and

[0181] c) 5-18% by weight of organic carrier,

[0182] The weight percentage is based on the total weight of the conductive paste.

[0183] Implementation Scheme 9. An electrode for a crystalline silicon solar cell, said electrode being formed by sintering the conductive paste described in Implementation Scheme 7 or 8.

[0184] Implementation Scheme 10. A crystalline silicon solar cell comprising a substrate and electrodes bonded to the substrate as described in Implementation Scheme 9.

[0185] Example

[0186] The present invention is illustrated below with examples, but it should be understood that the following embodiments are non-limiting and are not intended to limit the scope of protection of the present invention.

[0187] raw material

[0188] PbO, B2O3, SiO2, ZnO, MgO, Cu2O, WO3, Al2O3, TeO2, Li2O, Na2O, K2O, CaO, SrO, Bi2O3, MoO3, Yb2O3, CeO2, and PbF2 are 4N grade chemical reagents.

[0189] Silver powder (Ag) is a spherical powder with a particle size D50 of 1.8 μm.

[0190] The silicon wafers are 182*182mm PERC monocrystalline silicon wafers, 182*182mm TOPCon monocrystalline silicon wafers, and 182*182mm BC monocrystalline silicon wafers.

[0191] The organic carrier (V1) has the following composition:

[0192] Saturated polyester resins with a molecular weight of 10,000 to 30,000: 2.0% by weight;

[0193] Polyvinyl butyral: 1.0% by weight;

[0194] Diethylene glycol butyl ether acetate: 4.8% by weight;

[0195] Alcohol ester twelve: 0.5 by weight;

[0196] Dimethyl silicone oil: 0.2% by weight

[0197] The weight percentages mentioned are based on the weight of the conductive paste.

[0198] Test methods

[0199] IV tests were performed on the solar cells using the commercial IV tester “cetisPV-Celltest4-BF” from Halm Elektronik GmbH to measure the cell conversion efficiency (Eta), open circuit voltage (Voc), short circuit current (Isc), reverse current (Irev2), fill factor (FF), parallel resistance (Rsh), and series resistance (Rs).

[0200] Preparation of glass powder

[0201] • Calculate the mass of the raw materials used according to the molar ratio of the substances described in Table 1, weigh them and mix them evenly;

[0202] • Melt the mixed raw materials in a platinum crucible in a muffle furnace at 1100°C for 30 minutes;

[0203] • Pour the molten glass into a cold rolling mill and rapidly cool it to below 100°C to obtain glass slag;

[0204] • Place the glass slag in a ball mill and coarsely grind for 30 minutes to obtain coarse powder;

[0205] • The coarse powder was ground and classified using an air jet mill to obtain glass powder with a particle size D50 = 1.5 μm.

[0206] Table 1 Composition of glass powder

[0207] Preparation of conductive paste (Examples 1-2 / Comparative Examples 1-2)

[0208] According to the proportions shown in Table 2, weigh out the silver powder, glass powder and organic carrier respectively, combine them, mix them with a planetary mixer, and then mix them with a three-roll mill to obtain the conductive paste of Examples 1-2 / Comparative Examples 1-2.

[0209] Table 2 Composition of Conductive Paste

[0210] Preparation of solar cell substrates (cells) with electrodes (Samples 1-2 of this invention / Comparative Samples 1-2)

[0211] The conductive pastes of Examples 1-2 and Comparative Examples 1-2 were screen-printed (430-11-3.5-11-9BB screen) onto 182*182mm PERC monocrystalline silicon wafers to form fine grids on the front (illuminated side). After all grid lines were printed, they were dried and then rapidly sintered at a peak temperature of 800℃ with a time of 16 seconds from room temperature to peak temperature to obtain solar cell substrates with electrodes (Samples 1-2 of the present invention and Comparative Samples 1-2). The electrical performance was then tested. The results of Samples 1-2 of the present invention and Comparative Sample 1 are shown in Table 3. However, the electrical performance of Comparative Sample 2, prepared using GA1 single glass powder, was very poor and not comparable to Samples 1 and 2 of the present invention.

[0212] Table 3 Performance of Solar Cells

[0213] As can be seen from the results in Table 3, the fill factor FF of the solar cell of the present invention, which uses a combination of two glass powders, is superior to that of the comparative sample which uses a single glass powder. The overall electrical performance Eta of the solar cell of the present invention also shows a significant advantage.

[0214] Furthermore, by comparing the SEM images of the comparative sample 2 (Fig. 1a and Fig. 1b) with the SEM images of the present invention sample 1 (Fig. 2a and Fig. 2b), it can be found that the passivation layer of the present invention sample is uniformly eroded, while the comparative sample 2 has a poor erosion effect.

[0215] Preparation of glass powder

[0216] • Calculate the mass of the raw materials used according to the molar ratio of the substances described in Table 4, weigh them and mix them evenly;

[0217] • Melt the mixed raw materials in a platinum crucible in a muffle furnace at 1100°C for 30 minutes;

[0218] • Pour the molten glass into a cold rolling mill and rapidly cool it to below 100°C to obtain glass slag;

[0219] • Place the glass slag in a ball mill and coarsely grind for 30 minutes to obtain coarse powder;

[0220] • The coarse powder was ground and classified using an air jet mill to obtain glass powder with a particle size D50 = 1.5 μm.

[0221] Table 4 Composition of glass powder

[0222] Preparation of conductive paste (Examples 3-4 / Comparative Example 3)

[0223] According to the proportions shown in Table 5, weigh out the silver powder, glass powder and organic carrier respectively, combine them, mix them with a planetary mixer, and then mix them with a three-roll mill to obtain the conductive paste of Examples 3-4 / Comparative Example 3.

[0224] Table 5 Composition of Conductive Paste

[0225] Preparation of solar cell substrates (cells) with electrodes (Samples 3-4 of this invention / Comparative Sample 3)

[0226] The conductive pastes of Examples 3-4 and Comparative Example 3 were screen-printed onto 182*182mm TOPCon monocrystalline silicon wafers using a 430-11-15-3.5-14-9BB screen to form back (backlight) fine grids. After all grid lines were printed, they were dried and then rapidly sintered at a peak temperature of 720℃ with a time of 16 seconds from room temperature to peak temperature to obtain solar cell substrates with electrodes (Samples 3-4 of this invention and Comparative Example 3). The electrical performance was then tested, and the results are shown in Table 6.

[0227] Table 6 Performance of Solar Cells

[0228] As can be seen from the results in Table 6, the fill factor FF of the solar cell of the present invention, which uses a combination of two glass powders, is superior to that of the comparative sample which uses a single glass powder. The overall electrical performance Eta of the solar cell of the present invention also shows a significant advantage.

[0229] Preparation of glass powder

[0230] • Calculate the mass of the raw materials used according to the molar ratio of the substances described in Table 7, weigh them and mix them evenly;

[0231] • Melt the mixed raw materials in a platinum crucible in a muffle furnace at 1100°C for 30 minutes;

[0232] • Pour the molten glass into a cold rolling mill and rapidly cool it to below 100°C to obtain glass slag;

[0233] • Place the glass slag in a ball mill and coarsely grind for 30 minutes to obtain coarse powder;

[0234] • The coarse powder was ground and classified using an air jet mill to obtain glass powder with a particle size D50 = 1.5 μm.

[0235] Table 7 Composition of glass powder

[0236] Preparation of conductive paste (Examples 5-6 / Comparative Example 4)

[0237] According to the proportions shown in Table 8, weigh out the silver powder, glass powder and organic carrier respectively, combine them, mix them with a planetary mixer, and then mix them with a three-roll mill to obtain the conductive paste of Examples 5-6 / Comparative Example 4.

[0238] Table 8 Composition of Conductive Paste

[0239] Fabrication of solar cell substrates with electrodes (Samples 5-6 of this invention / Comparative Sample 4)

[0240] The conductive pastes of Examples 5-6 and Comparative Example 4 were screen-printed (430-11-15-3.5-18-11BB screen) onto 182*182mm BC monocrystalline silicon wafers to form N-region contact fine grids. After all grid lines were printed, they were dried and then rapidly sintered at a peak temperature of 700℃ and a time from room temperature to peak temperature of 16 seconds to obtain solar cell substrates (cells) with electrodes (Samples 5-6 of this invention and Comparative Sample 4). The electrical performance was tested, and the results are shown in Table 9.

[0241] Table 9 Performance of Solar Cells

[0242] As can be seen from the results in Table 9, the fill factor FF of the solar cell of the present invention, which uses a combination of two glass powders, is superior to that of the comparative sample which uses a single glass powder. The overall electrical performance Eta of the solar cell of the present invention also shows a significant advantage.

[0243] Although specific embodiments of the invention have been shown and described, it should be understood that other modifications, alternatives, and alternatives are known to those skilled in the art. Such modifications, alternatives, and alternatives may be made without departing from the spirit and scope of the invention as defined by the appended claims. Various features of the invention are described in the appended claims.

Claims

1. A glass powder composition comprising: a) First glass powder, and b) Second glass powder, The first glass powder contains: 30-50 mol% TeO2, 15-35 mol% Li₂O, 5-30 mol% of at least two oxides selected from SiO2, Bi2O3, Na2O, K2O, SrO, CaO, ZnO, MoO3, WO3 and Cu2O, At least one oxide selected from MgO, Al2O3, Yb2O3, Ta2O5, Y2O3, ZrO2, CeO2, and BaO, greater than 0 and less than 5 mol%. 0-25 mol% PbO, 0-10 mol% of B2O3, and 0-10 mol% of fluorine-containing compounds, The molar percentages mentioned therein are based on the total number of moles of all compounds in the first glass powder; The second glass powder contains: 10-35 mol% SiO2, 15-35 mol% PbO, 5-30 mol% of at least one oxide selected from Bi₂O₃, Na₂O, K₂O, SrO, CaO, ZnO, MoO₃, WO₃, Cu₂O, and B₂O₃. 0-40 mol% TeO2, and 0-15 mol% Li₂O, The molar percentages mentioned therein are based on the total number of moles of all compounds in the second glass powder.

2. The glass powder composition according to claim 1, wherein the first glass powder comprises 10-25 mol% PbO and 0.5-3 mol% B2O3.

3. The glass powder composition according to claim 1 or 2, wherein the fluorine-containing compound includes PbF2, NaF, LiF, KF, CaF2, ZnF2, NaBF4, LiBF4, YF3, YOF and combinations thereof, preferably PbF2, NaF, LiF, KF, and CaF2, and more preferably PbF2 and NaF.

4. The glass powder composition according to any one of claims 1-3, wherein the second glass powder comprises 20-40 mol% TeO2 and 5-15 mol% Li2O.

5. The glass powder composition according to any one of claims 1-4, wherein the first glass powder and the second glass powder each independently have a particle size D50 of 0.1-10 μm, preferably 0.2-7.0 μm, more preferably 0.6-2.5 μm.

6. The glass powder composition according to any one of claims 1-5, wherein the ratio of the first glass powder to the second glass powder in the glass powder composition is from 7:1 to 1:3 by weight.

7. A conductive paste comprising: a) Silver powder, b) The glass powder composition according to any one of claims 1-6, and c) Organic carrier.

8. The conductive paste according to claim 7, wherein the conductive paste comprises: a) 80-93% by weight of silver powder, b) 1-10% by weight of a glass powder composition, and c) 5-18% by weight of organic carrier, The weight percentage is based on the total weight of the conductive paste.

9. An electrode for a crystalline silicon solar cell, said electrode being formed by sintering the conductive paste of claim 7 or 8.

10. A crystalline silicon solar cell comprising a substrate and an electrode as claimed in claim 9 bonded to the substrate.

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