A paste and battery for double-sided poly solar cells

Abstract

The present application provides a paste for double-sided poly solar cells, including a conductive paste for the front fine grid and a conductive paste for the back fine grid, which serve as the sintering raw materials for the front passivation layer and the back passivation layer of the double-sided poly solar cell, respectively. The four glass powders in the front conductive paste play different roles; the etching effect of the paste can be adjusted, which not only ensures a good contact effect, but also causes less damage to the front poly layer, thereby protecting the passivation effect of the front poly layer. The four glass powders in the back paste can etch the silicon nitride and aluminum oxide on the back of the battery, avoiding excessive damage to the poly layer, so that the battery efficiency can be further improved. The paste provided in the present application solves the problem of excessive damage to the poly layer during the sintering process of double-sided poly solar cells while ensuring good contact effects. The present application also provides a double-sided poly solar cell, which uses the paste provided in the present application to sinter the front and back of the battery respectively.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a paste and a battery for double-sided poly solar cells. Background Art

[0002] Double-sided Poly technology, also known as double-sided polysilicon technology, uses a poly layer on the front side of the cell to further reduce the carrier recombination rate on the cell surface and reduce contact resistance, thereby further improving cell efficiency. The core of double-sided Poly technology lies in the use of polycrystalline silicon. Polycrystalline silicon has long been one of the main materials for photovoltaic cells due to its high photoelectric conversion efficiency and low production cost.

[0003] Generally speaking, sintering is the process of heating powder or powder compact to a temperature below the melting point of its constituents, followed by cooling to room temperature using a specific method and speed. The sintering process for solar cells is similar, being closely linked to the screen printing process. The quality of sintering directly impacts the quality of screen printing. The sintering process primarily ensures that the screen-printed positive and negative electrodes form a good ohmic contact with the silicon wafer at high temperatures, thereby improving the solar cell's open-circuit voltage and fill factor. It also provides good passivation for the solar cell, boosting its conversion efficiency. Bifacial poly (polyethylene) solar cells also have a poly (polyethylene) layer on the front side, which serves as a passivation layer. However, during current sintering of the front side of bifacial poly (polyethylene) solar cells, glass frit deeply etches the front side, severely damaging the poly layer and rendering the passivation layer ineffective. Furthermore, the front and back sides of bifacial poly (polyethylene) solar cells have different structures, so using the same silver paste for sintering cannot achieve the desired effect on both sides.

[0004] In order to solve the problem of excessive damage to the poly layer during the sintering process of double-sided poly solar cells while ensuring good contact effects, the present application provides a slurry and a cell for double-sided poly solar cells. Summary of the Invention

[0005] In order to solve the problem of excessive damage to the poly layer during the sintering process of double-sided poly solar cells while ensuring good contact effect, the present application provides a slurry for double-sided poly solar cells, which includes a conductive paste for the front fine grid and a conductive paste for the back fine grid.

[0006] The slurry provided in this application can be used specifically in double-sided poly solar cells. Different slurries are sintered on the front and back of the cell. While ensuring good contact effect during the sintering process, there is a problem of excessive damage to the poly layer.

[0007] The conductive paste for the front fine grid includes a front conductive phase, front glass frit, a front organic phase, and front additives. The front glass frit includes a first front glass frit, a second front glass frit, a third front glass frit, and a fourth front glass frit. The first front glass frit is a Pb-Si-B-Al-Zn glass frit, the second front glass frit is a P-Pb-Si-B-Bi-Ca-Al glass frit, the third front glass frit is a Si-B-Ca-Ba-Zn glass frit, and the fourth front glass frit is a Bi-Cu-Pb-Si-B glass frit.

[0008] The conductive paste of the back fine grid includes back glass powder, and the back glass powder includes first back glass powder, second back glass powder, third back glass powder and fourth back glass powder. The first back glass powder is Te-Pb-Si-B-Al-Zn series glass powder, the second back glass powder is Te-Pb-Si-B-Bi-Ca-W-Mn series glass powder, the third back glass powder is Si-B-Ca-Ba-Zn series glass powder, and the fourth back glass powder is Bi-Cu-Pb-Si-B series glass powder.

[0009] Optionally, the mass fraction of silver powder in the conductive paste of the front fine grid is 88%-90.5%, the mass fraction of the front organic phase is 5%-10%, and the mass fraction of the front additive is 0.1%-0.5%.

[0010] Optionally, the mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.3%-0.5%, the mass fraction of the second front glass powder is 1.2%-2.0%, the mass fraction of the third front glass powder is 0.2%-0.5%, and the mass fraction of the fourth front glass powder is 0.2%-0.4%.

[0011] Optionally, based on the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al, and 5% to 20% Zn; based on the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% to 10% P, 20% to 30% Pb, 10% to 20% Si, 10% to 25% B, 5% to 20% Bi, 5% to 15% A l, 5% to 20% Ca; based on the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 25% to 45% Si, 10% to 30% B, 10% to 20% Ca, 5% to 15% Ba, and 5% to 15% Zn; based on the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 30% to 45% Bi, 1% to 15Cu, 5% to 15% Pb, 10% to 30% Si, and 5% to 20% B.

[0012] Optionally, the glass transition temperature of the first front glass powder is 320-350°C, the glass transition temperature of the second front glass powder is 350-380°C, the glass transition temperature of the third front glass powder is 380-420°C, and the glass transition temperature of the fourth front glass powder is 420-480°C.

[0013] Optionally, based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 20% to 40% Te, 20% to 40% Pb, 10% to 20% Si, 5% to 20% B, 1% to 10% Al, and 5% to 15% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 10% to 30% Te, 15% to 30% Pb, 10% to 20% Si, 5% to 20% B, 5% to 15% Bi, and 5% to 15% Zn. %Ca, 1%~5%W, 1%~5%Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 25%~45%Si, 10%~30%B, 10%~20%Ca, 5%~15%Ba, and 5%~15%Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 30%~45%Bi, 1%~15%Cu, 5%~15%Pb, 10%~30%Si, and 5%~20%B.

[0014] Optionally, the glass transition temperature of the first back glass powder is 320-350°C, the glass transition temperature of the second back glass powder is 350-380°C, the glass transition temperature of the third back glass powder is 380-420°C, and the glass transition temperature of the fourth back glass powder is 420-480°C.

[0015] Optionally, the front additive includes ZnAl4 alloy powder, and the front organic phase includes resin, organic solvent and organic additive.

[0016] Optionally, the conductive paste for the back fine grid further includes a back conductive phase, a back organic phase, and a back additive. The back conductive phase includes silver powder, the back additive includes ZnAl4 alloy powder, and the back organic phase includes resin, organic solvent, and organic auxiliary agent. The conductive paste for the back fine grid has a silver powder mass fraction of 88% to 90.5%, a back organic phase mass fraction of 5% to 10%, and a back additive mass fraction of 0.1% to 0.5%.

[0017] On the other hand, the present application also provides a double-sided poly solar cell, which includes a front passivation layer and a back passivation layer, a front grid line is arranged on the front passivation layer, and the front grid line is prepared by the conductive silver paste of the front fine grid described in any of the above items, and a back grid line is arranged on the back passivation layer, and the back grid line is prepared by the conductive paste of the back fine grid described in any of the above items.

[0018] The present application provides a paste for a double-sided poly solar cell, including a conductive paste for the front fine grid and a conductive paste for the back fine grid, which are respectively used as the sintering raw materials for the front passivation layer and the back passivation layer of the double-sided poly solar cell. The conductive paste for the front fine grid and the conductive paste for the back fine grid each contain four types of glass powder.

[0019] The four types of glass powder in the front conductive paste play different roles. The etching effect of the paste can be adjusted, which not only ensures good contact effect, but also causes less damage to the front poly layer, thus protecting the passivation effect of the front poly layer. The four types of glass powder in the back paste can etch the silicon nitride and aluminum oxide on the back of the battery, while ensuring good contact effect, avoiding excessive damage to the poly layer, ensuring the passivation ability of the battery, and further improving the battery efficiency. The paste provided in this application solves the problem of excessive damage to the poly layer during the sintering process of double-sided poly solar cells while ensuring good contact effect.

[0020] The present application also provides a double-sided poly solar cell, and the slurry provided in the present application is used to sinter the front and back sides of the cell respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 Schematic diagram of the double-sided poly solar cell structure;

[0023] Figure 2 This is an electron microscope image of a double-sided poly solar cell prepared with silver paste in Example 1;

[0024] Figure 3 This is an electron microscope image of a double-sided poly solar cell prepared with silver paste in comparative example 1. DETAILED DESCRIPTION

[0025] The following embodiments are described in detail, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numbers in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following embodiments are not intended to represent all possible implementations consistent with the present application. They are merely examples of systems and methods consistent with certain aspects of the present application, as detailed in the claims.

[0026] To address the issue of excessive damage to the poly layer during the sintering process of bifacial poly solar cells while ensuring good contact, this application provides a slurry for bifacial poly solar cells, comprising a conductive slurry for the front fine grid and a conductive slurry for the back fine grid. The slurry provided in this application can be specifically used in bifacial poly solar cells, with the front and back of the cell sintered using different slurries.

[0027] The structure of double-sided poly solar cells, such as Figure 1 As shown, both sides of the silicon substrate are designed with poly layers. Starting from the silicon substrate layer, the front structure is SiO2 layer, Poly layer and SiN X Layer (front passivation layer), the back structure is SiO2 layer, Poly layer Al2O3 layer and SiN X layer.

[0028] In some embodiments, the conductive paste for the front fine grid includes a front conductive phase, a front glass frit, a front organic phase, and a front additive. The front glass frit includes a first front glass frit, a second front glass frit, a third front glass frit, and a fourth front glass frit. The first front glass frit is a Pb-Si-B-Al-Zn glass frit, the second front glass frit is a P-Pb-Si-B-Bi-Ca-Al glass frit, the third front glass frit is a Si-B-Ca-Ba-Zn glass frit, and the fourth front glass frit is a Bi-Cu-Pb-Si-B glass frit.

[0029] In some embodiments, the conductive paste of the back fine grid includes a back glass powder, and the back glass powder includes a first back glass powder, a second back glass powder, a third back glass powder and a fourth back glass powder. The first back glass powder is a Te-Pb-Si-B-Al-Zn series glass powder, the second back glass powder is a Te-Pb-Si-B-Bi-Ca-W-Mn series glass powder, the third back glass powder is a Si-B-Ca-Ba-Zn series glass powder, and the fourth back glass powder is a Bi-Cu-Pb-Si-B series glass powder.

[0030] In some embodiments, the mass fraction of silver powder in the conductive paste of the front fine grid is 88%-90.5%, the mass fraction of the front organic phase is 5%-10%, and the mass fraction of the front additive is 0.1%-0.5%.

[0031] In some embodiments, the mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.3%-0.5%, the mass fraction of the second front glass powder is 1.2%-2.0%, the mass fraction of the third front glass powder is 0.2%-0.5%, and the mass fraction of the fourth front glass powder is 0.2%-0.4%.

[0032] Glass powder is a crucial additive in conductive pastes, primarily enhancing the adhesion and conductivity of the silver paste. It also improves the fluidity of the silver paste, promoting its even distribution across the cell surface, thereby increasing the photovoltaic conversion efficiency of solar cells. Despite its low content, glass powder plays a crucial role in the paste, corroding the silicon nitride layer, forming the electrode, and bridging the electron transport process. Glass powder requires careful balancing and adjustment under varying conditions, performing crucial functions such as bonding the silver powder, lowering the sintering temperature, corroding the anti-reflective layer on the silicon substrate, and forming an ohmic contact.

[0033] In some embodiments, based on the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al, and 5% to 20% Zn; based on the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% to 10% P, 20% to 30% Pb, 10% to 20% Si, 10% to 25% B, 5% to 20% Bi, 5% to 15 %Al, 5%~20%Ca; based on the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 25%~45%Si, 10%~30%B, 10%~20%Ca, 5%~15%Ba, and 5%~15%Zn; based on the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 30%~45%Bi, 1%~15Cu, 5%~15%Pb, 10%~30%Si, and 5%~20%B.

[0034] In some embodiments, the glass transition temperature of the first front glass powder is 320-350°C, the glass transition temperature of the second front glass powder is 350-380°C, the glass transition temperature of the third front glass powder is 380-420°C, and the glass transition temperature of the fourth front glass powder is 420-480°C.

[0035] First, the lead content in the front glass powder is high, resulting in strong etching ability and good etching results. It mainly etches the silicon nitride and aluminum oxide passivation layers. The amount added should not be too much, as too much can easily damage the Poly layer, resulting in a loss of opening voltage. Second, the lead content in the front glass powder is low, with a transition temperature of 350-380°C. Due to the addition of the P element, it can soften better during sintering and has better fluidity, which can promote the uniform distribution of the glass powder, thereby driving a better uniform distribution of the silver powder. Its large addition amount plays a role in assisting in etching the passivation layer. At the same time, its etching ability has little damage to the Poly layer, which can protect the Poly layer to a certain extent. Third, some elements that can dissolve oxygen on the silver surface are added to the front glass powder, which can better dissolve silver and improve the contact between silver and silicon wafers. The transition temperature of the fourth front glass powder is higher than that of other glass powders, which can promote sintering. The fourth front glass powder melts later and leaves more residue in the silver. The glass powder will shrink during sintering, which will shrink and densify the silver, reducing the holes in the silver grid and increasing the density, thereby reducing the line resistance, reducing electron transmission loss, and improving the photoelectric conversion efficiency.

[0036] In some embodiments, based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 20% to 40% Te, 20% to 40% Pb, 10% to 20% Si, 5% to 20% B, 1% to 10% Al, and 5% to 15% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 10% to 30% Te, 15% to 30% Pb, 10% to 20% Si, 5% to 20% B, 5% to 15% Bi, and 5% to 15% Ca, 1% to 5% W, 1% to 5% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 25% to 45% Si, 10% to 30% B, 10% to 20% Ca, 5% to 15% Ba, and 5% to 15% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 30% to 45% Bi, 1% to 15% Cu, 5% to 15% Pb, 10% to 30% Si, and 5% to 20% B.

[0037] In some embodiments, the glass transition temperature of the first back glass powder is 320-350°C, the glass transition temperature of the second back glass powder is 350-380°C, the glass transition temperature of the third back glass powder is 380-420°C, and the glass transition temperature of the fourth back glass powder is 420-480°C.

[0038] First, the backside glass powder has high tellurium and lead content, resulting in strong etching ability and excellent etching results. It primarily etches the silicon nitride and aluminum oxide passivation layers. Excessive addition should be avoided, as this can easily damage the poly layer, leading to a loss in opening voltage. Second, the backside glass powder has low tellurium and lead content, and the use of lead and bismuth in combination reduces damage to the poly layer. Its transition temperature is 350-380°C. The addition of W and Mn enhances softening and fluidity during sintering, promoting uniform distribution of the glass powder and, in turn, silver powder. Its high addition aids in etching the passivation layer, while its etching ability minimizes damage to the poly layer, providing some protection. Third, the backside glass powder incorporates elements that dissolve oxygen on the silver surface, enhancing silver dissolution and ensuring better contact between the silver and the silicon wafer. The glass transition temperature of the fourth back glass powder is higher than that of other glass powders, which can promote sintering. In addition, the fourth glass powder melts later and leaves more residue in the silver. The glass powder will shrink during sintering, which will shrink and densify the silver, reducing the holes in the silver grid and increasing the density, thereby reducing the line resistance, reducing electron transmission loss, and improving the photoelectric conversion efficiency.

[0039] In some embodiments, the mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.3%-0.5%, the mass fraction of the second back glass powder is 1.2%-2.0%, the mass fraction of the third back glass powder is 0.2%-0.5%, and the mass fraction of the fourth back glass powder is 0.2%-0.4%.

[0040] In some embodiments, the front additive includes ZnAl4 alloy powder, and the front organic phase includes resin, organic solvent, and organic additive.

[0041] In some embodiments, the conductive paste for the back fine grid further includes a back conductive phase, a back organic phase, and a back additive. The back conductive phase includes silver powder, the back additive includes ZnAl4 alloy powder, and the back organic phase includes resin, an organic solvent, and an organic auxiliary agent. The conductive paste for the back fine grid has a silver powder mass fraction of 88% to 90.5%, a back organic phase mass fraction of 5% to 10%, and a back additive mass fraction of 0.1% to 0.5%.

[0042] In some embodiments, the front conductive phase and the back conductive phase comprise aluminum powder.

[0043] In some embodiments, the resin in the front conductive paste and the back conductive paste is one or more of a linear triblock copolymer, polyvinyl butyral ester or cellulose acetate butyrate; the organic solvent is one or more of butyl ether, methyl ester or acetate; and the organic additive is one or both of stearate or silicone oil.

[0044] Example 1:

[0045] This embodiment provides a paste for double-sided poly solar cells, namely, a first paste.

[0046] The first paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 88% silver powder, 9% of a solvent mixture of cellulose acetate butyrate, polyvinyl butyral, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder. The conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 88% silver powder, 9% of a solvent mixture of linear triblock copolymer, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder.

[0047] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.3%, the mass fraction of the second front glass powder is 1.7%, the mass fraction of the third front glass powder is 0.5%, and the mass fraction of the fourth front glass powder is 0.4%.

[0048] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 50% Pb, 20% Si, 5% B, 10% Al, and 15% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% P, 30% Pb, 20% Si, 10% B, 9% Bi, 15% Al, and 15% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 25% Si, 30% B, 15% Ca, 15% Ba, and 15% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 45% Bi, 15% Cu, 15% Pb, 10% Si, and 15% B.

[0049] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.3%, the mass fraction of the second back glass powder is 2.0%, the mass fraction of the third back glass powder is 0.4%, and the mass fraction of the fourth back glass powder is 0.2%.

[0050] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 40% Te, 20% Pb, 10% Si, 5% B, 10% Al, and 15% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 30% Te, 30% Pb, 20% Si, 5% B, 5% Bi, 5% Ca, 4% W, and 1% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 25% Si, 30% B, 20% Ca, 15% Ba, and 10% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 45% Bi, 15% Cu, 5% Pb, 30% Si, and 5% B.

[0051] Example 2:

[0052] This embodiment provides a paste for double-sided poly solar cells, namely, a second paste.

[0053] The second paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 89% silver powder, 7.6% of a linear triblock copolymer, an acetate, silicone oil, and a solvent mixture of diethylene glycol butyl ether acetate, and 0.5% ZnAl4 alloy powder; the conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 90.5% silver powder, 5.6% of a linear triblock copolymer, a solvent mixture of butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.5% ZnAl4 alloy powder.

[0054] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.5%, the mass fraction of the second front glass powder is 1.5%, the mass fraction of the third front glass powder is 0.5%, and the mass fraction of the fourth front glass powder is 0.4%.

[0055] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 30% Pb, 20% Si, 30% B, 10% Al, and 10% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 10% P, 20% Pb, 10% Si, 10% B, 20% Bi, 15% Al, and 15% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 45% Si, 30% B, 10% Ca, 5% Ba, and 10% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 45% Bi, 1% Cu, 11% Pb, 23% Si, and 20% B.

[0056] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.5%, the mass fraction of the second back glass powder is 2.0%, the mass fraction of the third back glass powder is 0.5%, and the mass fraction of the fourth back glass powder is 0.4%.

[0057] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 30% Te, 30% Pb, 10% Si, 20% B, 1% Al, and 9% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 15% Te, 30% Pb, 20% Si, 5% B, 5% Bi, 15% Ca, 5% W, and 5% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 45% Si, 15% B, 20% Ca, 5% Ba, and 15% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 45% Bi, 15% Cu, 15% Pb, 10% Si, and 15% B.

[0058] Example 3:

[0059] This embodiment provides a paste for double-sided poly solar cells, namely, a third paste.

[0060] The third paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 90% silver powder, 7.2% of a linear triblock copolymer, a solvent mixture of butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.3% ZnAl4 alloy powder. The conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 90% silver powder, 7.2% of a linear triblock copolymer, a solvent mixture of butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.3% ZnAl4 alloy powder.

[0061] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.4%, the mass fraction of the second front glass powder is 1.6%, the mass fraction of the third front glass powder is 0.3%, and the mass fraction of the fourth front glass powder is 0.2%.

[0062] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 50% Pb, 10% Si, 10% B, 10% Al, and 20% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% P, 30% Pb, 10% Si, 25% B, 20% Bi, 9% Al, and 5% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 45% Si, 25% B, 10% Ca, 15% Ba, and 5% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 30% Bi, 5% Cu, 15% Pb, 30% Si, and 20% B.

[0063] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.4%, the mass fraction of the second back glass powder is 1.6%, the mass fraction of the third back glass powder is 0.2%, and the mass fraction of the fourth back glass powder is 0.3%.

[0064] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 40% Te, 20% Pb, 20% Si, 5% B, 10% Al, and 5% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 10% Te, 25% Pb, 20% Si, 5% B, 15% Bi, 15% Ca, 5% W, and 5% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 45% Si, 10% B, 30% Ca, 10% Ba, and 5% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 30% Bi, 5% Cu, 15% Pb, 30% Si, and 20% B.

[0065] Example 4:

[0066] This embodiment provides a paste for double-sided poly solar cells, ie, a fourth paste.

[0067] The fourth paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 90.5% silver powder, 6.5% of a solvent mixture of polyvinyl butyral, methyl ester, silicone oil, stearate, and diethylene glycol butyl ether acetate, and 0.5% ZnAl4 alloy powder. The conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 90.5% silver powder, 6.5% of a solvent mixture of a linear triblock copolymer, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.5% ZnAl4 alloy powder.

[0068] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.5%, the mass fraction of the second front glass powder is 1.2%, the mass fraction of the third front glass powder is 0.5%, and the mass fraction of the fourth front glass powder is 0.3%.

[0069] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 50% Pb, 20% Si, 24% B, 1% Al, and 5% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 5% P, 20% Pb, 20% Si, 25% B, 5% Bi, 5% Al, and 20% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 45% Si, 10% B, 20% Ca, 10% Ba, and 15% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 45% Bi, 15% Cu, 5% Pb, 30% Si, and 5% B.

[0070] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.5%, the mass fraction of the second back glass powder is 1.5%, the mass fraction of the third back glass powder is 0.3%, and the mass fraction of the fourth back glass powder is 0.2%.

[0071] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 20% Te, 40% Pb, 10% Si, 5% B, 10% Al, and 15% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 19% Te, 15% Pb, 10% Si, 20% B, 15% Bi, 15% Ca, 1% W, and 5% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 45% Si, 25% B, 10% Ca, 15% Ba, and 5% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 45% Bi, 1% Cu, 15% Pb, 19% Si, and 20% B.

[0072] Embodiment 5:

[0073] This embodiment provides a paste for double-sided poly solar cells, ie, a fifth paste.

[0074] The fifth paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 90.5% silver powder, 5% of a solvent mixture of cellulose acetate butyrate, polyvinyl butyral, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder. The conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 88% silver powder, 10% of a solvent mixture of a linear triblock copolymer, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder.

[0075] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.2%, the mass fraction of the second front glass powder is 2.0%, the mass fraction of the third front glass powder is 0.2%, and the mass fraction of the fourth front glass powder is 0.4%.

[0076] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 50% Pb, 20% Si, 5% B, 10% Al, and 15% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% P, 30% Pb, 20% Si, 10% B, 9% Bi, 15% Al, and 15% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 25% Si, 30% B, 15% Ca, 15% Ba, and 15% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 45% Bi, 15% Cu, 15% Pb, 10% Si, and 15% B.

[0077] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.2%, the mass fraction of the second back glass powder is 1.2%, the mass fraction of the third back glass powder is 0.4%, and the mass fraction of the fourth back glass powder is 0.1%.

[0078] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 40% Te, 20% Pb, 10% Si, 5% B, 10% Al, and 15% Zn; based on the total molar percentage content of the second back glass powder as 100%, the second back glass powder includes 30% Te, 30% Pb, 20% Si, 5% B, 5% Bi, 5% Ca, 4% W, and 1% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 25% Si, 30% B, 20% Ca, 15% Ba, and 10% Zn; based on the total molar percentage content of the fourth back glass powder as 100%, the fourth back glass powder includes 45% Bi, 15% Cu, 5% Pb, 30% Si, and 5% B.

[0079] Example 6:

[0080] This embodiment provides a paste for double-sided poly solar cells, ie, a sixth paste.

[0081] The sixth paste includes a conductive paste for the front fine grid and a conductive paste for the back fine grid. The conductive paste for the front fine grid, based on the total mass percentage of the conductive paste, comprises 88% silver powder, 10% of a solvent mixture of cellulose acetate butyrate, polyvinyl butyral, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder. The conductive paste for the back fine grid, based on the total mass percentage of the conductive paste, comprises 90.5% silver powder, 5% of a solvent mixture of a linear triblock copolymer, butyl ether, stearate, and diethylene glycol butyl ether acetate, and 0.1% ZnAl4 alloy powder.

[0082] The mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.2%, the mass fraction of the second front glass powder is 0.8%, the mass fraction of the third front glass powder is 0.5%, and the mass fraction of the fourth front glass powder is 0.4%.

[0083] Taking the total molar percentage content of the first front glass powder as 100%, the first front glass powder includes 50% Pb, 20% Si, 5% B, 10% Al, and 15% Zn; taking the total molar percentage content of the second front glass powder as 100%, the second front glass powder includes 1% P, 30% Pb, 20% Si, 10% B, 9% Bi, 15% Al, and 15% Ca; taking the total molar percentage content of the third front glass powder as 100%, the third front glass powder includes 25% Si, 30% B, 15% Ca, 15% Ba, and 15% Zn; taking the total molar percentage content of the fourth front glass powder as 100%, the fourth front glass powder includes 45% Bi, 15% Cu, 15% Pb, 10% Si, and 15% B.

[0084] The mass fraction of the first back glass powder in the conductive paste of the back fine grid is 0.5%, the mass fraction of the second back glass powder is 2.0%, the mass fraction of the third back glass powder is 0.4%, and the mass fraction of the fourth back glass powder is 0.2%.

[0085] Based on the total molar percentage content of the first back glass powder as 100%, the first back glass powder includes 40% Te, 20% Pb, 10% Si, 5% B, 10% Al, and 15% Zn; based on the total molar percentage content of the sixth back glass powder as 100%, the second back glass powder includes 30% Te, 30% Pb, 20% Si, 5% B, 5% Bi, 5% Ca, 4% W, and 1% Mn; based on the total molar percentage content of the third back glass powder as 100%, the third back glass powder includes 25% Si, 30% B, 20% Ca, 15% Ba, and 10% Zn; based on the total molar percentage content of the sixth back glass powder as 100%, the sixth back glass powder includes 45% Bi, 15% Cu, 5% Pb, 30% Si, and 5% B.

[0086] Pastes prepared in Examples 1, 2, 3, 4, 5, 6, Comparative Example 1 (conventional silver paste JK03), and Comparative Example 2 (conventional silver paste JK04) were printed on both sides of a silicon wafer using a printing press. The glass frit in the conductive pastes in conventional silver pastes JK03 and JK04 consisted solely of Pb-Si-B glass frit. The rest of the conductive pastes in Comparative Examples 1 and 2 were identical to those in Example 1.

[0087] During printing, each paste was printed with the same wet weight, and 100 pieces of each conductive paste were printed. The cells were sintered in a sintering furnace to obtain double-sided poly solar cells. The photoelectric conversion efficiency of the cells was tested and the data was recorded. The test results are shown in Table 1, and the scanning electron microscope images are shown in Table 1. Figure 2 and Figure 3 shown.

[0088] Table 1 Cell test results

[0089] slurry Photoelectric conversion efficiency% Example 1 25.89 Example 2 26.12 Example 3 26.03 Example 4 25.98 Example 5 25.92 Example 6 25.96 Comparative Example 1 25.54 Comparative Example 2 25.58

[0090] As shown in Table 1 above, the photoelectric conversion efficiency of bifacial poly solar cells produced using conventional silver paste comparisons JK03 and JK04 is approximately 25.5%, while the photoelectric conversion efficiency of bifacial poly solar cells produced using the conductive pastes provided in various embodiments of the present invention is 26.0%. The silver pastes provided in this application have a significant effect on improving the photoelectric conversion efficiency of bifacial poly solar cells.

[0091] Figure 2 This is an electron microscope image of a battery prepared with silver paste according to Example 1 of this application. The pyramid morphology is basically intact, and the shiny edges of the pyramids indicate good contact. AgSi ions diffuse into each other to form good ohmic contact. Figure 3 This is the electron microscope image of the battery prepared with silver paste in comparative example 1. Figure 3 The pyramids on the surface of the battery shown are severely etched, the peak shape has been destroyed, the AgSi contact interface has less mutual diffusion, and the contact is poor.

[0092] The present application provides a paste for a double-sided poly solar cell, including a conductive paste for the front fine grid and a conductive paste for the back fine grid, which are respectively used as the sintering raw materials for the front passivation layer and the back passivation layer of the double-sided poly solar cell. The conductive paste for the front fine grid and the conductive paste for the back fine grid each contain four types of glass powder.

[0093] The four types of glass powder in the front conductive paste play different roles. The etching effect of the paste can be adjusted, which not only ensures good contact effect, but also causes less damage to the front poly layer, thus protecting the passivation effect of the front poly layer. The four types of glass powder in the back paste can etch the silicon nitride and aluminum oxide on the back of the battery, while ensuring good contact effect, avoiding excessive damage to the poly layer, ensuring the passivation ability of the battery, and further improving the battery efficiency. The paste provided in this application solves the problem of excessive damage to the poly layer during the sintering process of double-sided poly solar cells while ensuring good contact effect.

[0094] The present application also provides a double-sided poly solar cell, and the slurry provided in the present application is used to sinter the front and back sides of the cell respectively.

[0095] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without expending creative work shall fall within the scope of protection of this application.

Claims

1. A double-sided poly solar cell, characterized in that: The battery comprises a front passivation layer and a back passivation layer, a front grid line is arranged on the front passivation layer, and the front grid line is prepared by a conductive silver paste of a front fine grid; a back grid line is arranged on the back passivation layer, and the back grid line is prepared by a conductive paste of the back fine grid; the conductive paste of the front fine grid comprises a front conductive phase, a front glass powder, a front organic phase and a front additive; the front glass powder comprises a first front glass powder, a second front glass powder, a third front glass powder and a fourth front glass powder; based on the total mass percentage content of the conductive paste of the front fine grid being 100%, the mass fraction of the first front glass powder in the conductive paste of the front fine grid is 0.3%-0.5%, the mass fraction of the second front glass powder is 1.2%-2.0%, the mass fraction of the third front glass powder is 0.2%-0.5%, and the mass fraction of the fourth front glass powder is 0.2%-0.4%; based on the total molar percentage content of the first front glass powder, the second front glass powder, the third front glass powder and the fourth front glass powder being 100%, the first front glass powder comprises 30%-50% of the first front glass powder; Pb, 10%~20% Si, 5%~30% B, 1%~10% Al, 5%~20% Zn, the second front glass powder includes 1%~10% P, 20%~30% Pb, 10%~20% Si, 10%~25% B, 5%~20% Bi, 5%~15% Al, 5%~20% Ca, the third front glass powder includes 25%~45% Si, 10%~30% B, 10%~20% Ca, 5%~15% Ba, 5%~15% Zn, the fourth front glass powder includes 30%~45% Bi, 1%~15 Cu, 5%~15% Pb, 10%~30 Si, 5%~20 B; The conductive paste of the back fine grid includes back glass powder, which includes a first back glass powder, a second back glass powder, a third back glass powder, and a fourth back glass powder. Based on the total weight percentage of the conductive paste of the back fine grid as 100%, the weight percentage of the first back glass powder in the conductive paste of the back fine grid is 0.3%-0.5%, the weight percentage of the second back glass powder is 1.2%-2.0%, the weight percentage of the third back glass powder is 0.2%-0.5%, and the weight percentage of the fourth back glass powder is 0.2%-0.4%, respectively, based on the total molar percentage content of the first back glass powder, the second back glass powder, the third back glass powder and the fourth back glass powder being 100%, the first back glass powder includes 20%~40% Te, 20%~40% Pb, 10%~20% Si, 5%~20% B, 1%~10% Al, and 5%~15% Zn, the second back glass powder includes 10%~30% Te, 15%~30% Pb, 10%~20% Si, 5%~20% B, 1%~10% Al, and 5%~15% Zn. Si, 5%~20% B, 5%~15% Bi, 5%~15% Ca, 1%~5% W, 1%~5% Mn; the third back glass frit includes 25%~45% Si, 10%~30% B, 10%~20% Ca, 5%~15% Ba, 5%~15% Zn; the fourth back glass frit includes 30%~45% Bi, 1%~15% Cu, 5%~15% Pb, 10%~30% Si, 5%~20% B.

2. The battery according to claim 1, characterized in that The front conductive phase includes silver powder. The mass fraction of the silver powder in the conductive paste of the front fine grid is 88%-90.5%, the mass fraction of the front organic phase is 5%-10%, and the mass fraction of the front additive is 0.1%-0.5%.

3. The battery according to claim 1, characterized in that The glass transition temperature of the first front glass powder is 320~350℃, the glass transition temperature of the second front glass powder is 350~380℃, the glass transition temperature of the third front glass powder is 380~420℃, and the glass transition temperature of the fourth front glass powder is 420~480℃.

4. The battery according to claim 1, characterized in that The glass transition temperature of the first back glass powder is 320~350℃, the glass transition temperature of the second back glass powder is 350~380℃, the glass transition temperature of the third back glass powder is 380~420℃, and the glass transition temperature of the fourth back glass powder is 420~480℃.

5. The battery according to claim 1, characterized in that The front additive includes ZnAl4 alloy powder, and the front organic phase includes resin, organic solvent and organic additive.

6. The battery according to claim 1, characterized in that The conductive paste of the back fine grid further includes a back conductive phase, a back organic phase and a back additive.

7. The battery according to claim 6, characterized in that The back conductive phase includes silver powder.

8. The battery according to claim 7, characterized in that The back side additive includes ZnAl4 alloy powder.

9. The battery according to claim 8, characterized in that The back organic phase includes resin, organic solvent and organic auxiliary agent.

10. The battery according to claim 9, characterized in that The mass fraction of silver powder in the conductive paste of the back fine grid is 88%-90.5%, the mass fraction of the back organic phase is 5%-10%, and the mass fraction of the back additive is 0.1%-0.5%.

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