A P-zone conductive paste for xBC battery, preparation method, electrode and battery

Abstract

The present invention relates to a P-zone conductive paste for an xBC battery, comprising the following components: 83-86wt% silver powder, 3-7wt% glass powder, 0.5-3.5wt% aluminum powder, 0.5-3wt% additive, and the balance being an organic carrier; the silver powder is a mixture of at least two of micron-grade spherical silver powder, nano-grade spherical silver powder, and flaky silver powder, and the nano-grade spherical silver powder accounts for no more than 20% of the total mass of the silver powder. The present invention also relates to a method for preparing the conductive paste, and an electrode and a battery based on the conductive paste.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic cells and conductive pastes, and in particular to a P-zone conductive paste for an xBC cell, a preparation method, an electrode and a cell. Background Art

[0002] BC is the abbreviation of Back Contact, which means back-contact photovoltaic cells; there are many types of BC cells, such as PBC, IBC, HBC, etc., collectively referred to as xBC cells. Compared with existing TOPCon cells, HJT cells, etc., the biggest feature of xBC is that there is no grid line on the front, and the back is no longer a simple N area or P area, but usually a staggered P and N areas are prepared on the back of the battery, so that the positive and negative electrodes are integrated on the back of the battery. Thanks to this structure, there will be no electrode grid lines blocking the front of the xBC battery, which not only improves the power generation efficiency but also improves the aesthetics of the front. Because BC batteries adopt a design without metal grid lines on the front, the power generation per watt is usually about 2% to 3% higher than that of TOPCon batteries.

[0003] At present, the problem faced by the P-region electrode of the xBC battery is the poor ohmic contact effect, and both the contact resistance and the body resistance are large; in addition, since the N-type silicon wafer has a longer body life, it can ensure that the non-equilibrium carriers can smoothly reach the back pn junction area before recombination. Therefore, most of the current BC batteries use N-type silicon wafers as substrates, and the passivation layer of the P-region on the back of the substrate is difficult to corrode, and the "window opening" effect is poor, which further affects the effect of the ohmic contact. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a P-zone conductive paste for xBC battery, a preparation method, an electrode and a battery. The technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a P-zone conductive paste for an xBC battery, which comprises the following components:

[0006] Silver powder 83-86wt%, glass powder 3-7wt%, aluminum powder 0.5-3.5wt%, additives 0.5-3wt%, and the balance is an organic carrier;

[0007] The silver powder is a mixture of at least two of micron-sized spherical silver powder, nano-sized spherical silver powder and flaky silver powder, and the nano-sized spherical silver powder accounts for no more than 20% of the total mass of the silver powder.

[0008] In one possible implementation,

[0009] The silver powder is a mixture of micron-sized spherical silver powder, nano-sized spherical silver powder and flaky silver powder, wherein the mass proportion of the micron-sized spherical silver powder is 70-80%, the mass proportion of the flaky silver powder is 10-20%, and the mass proportion of the nano-sized spherical silver powder is 5-15%;

[0010] The D50 particle size of the micron-sized spherical silver powder and the flaky silver powder is 0.8 to 2.5 μm;

[0011] The particle size of the nano-scale spherical silver powder is 500-800nm.

[0012] In one possible implementation,

[0013] The aluminum powder is specifically micron-grade spherical aluminum powder, and its D50 particle size is 0.5 to 6 μm.

[0014] In the above possible implementation, further,

[0015] The D50 particle size of the aluminum powder is 2.5 μm.

[0016] In one possible implementation,

[0017] The glass powder includes a first glass powder and a second glass powder; based on the total mass of the conductive paste:

[0018] The first glass powder comprises 35-60 wt % of Bi2O3, 25-40 wt % of B2O3, and 5-20 wt % of SiO2;

[0019] The second glass powder is a mixture of at least two of BaO, ZnO, GaO, K2O, and Na2O; the mass percentage of the second glass powder is 8 to 12 wt%.

[0020] In one possible implementation,

[0021] The additive is a mixture of WO3, metal fluoride and silane coupling agent; based on the total mass of the additive:

[0022] The content of WO3 is 30-50wt%;

[0023] The metal fluoride content is 10-15wt%;

[0024] The content of the silane coupling agent is 30-45 wt %.

[0025] In a possible implementation, the organic carrier includes a mixed solvent and a resin;

[0026] The mixed solvent is a mixture of terpineol and butyl carbitol and / or citric acid, and the mass proportion of the terpineol is ≥60%;

[0027] Based on the total mass of the organic carrier, the resin includes 5-8wt% of ethyl cellulose, 0-5wt% of Span series and / or Tween series, 1.5-2.5wt% of sodium dodecylbenzene sulfonate, and 0.2-0.8wt% of polyamide.

[0028] In a second aspect, the present invention provides a method for preparing the above conductive paste, comprising the following steps:

[0029] S1, dispersing and mixing the silver powder and the additive uniformly, then adding the aluminum powder, dispersing and mixing uniformly to obtain a first product;

[0030] S2, mixing the glass powder and the organic carrier uniformly to obtain a second product;

[0031] S3. Mix the first product and the second product, and stir them thoroughly to obtain the conductive paste.

[0032] In a third aspect, the present invention provides a P-region electrode on the back side of an xBC battery, which is prepared by a metallization process using the above-mentioned conductive paste.

[0033] In a fourth aspect, the present invention provides an xBC battery, wherein the P-region electrode on the back side thereof adopts the above-mentioned electrode.

[0034] The above technical solution provided by this application has at least the following technical effects or advantages:

[0035] The conductive paste disclosed in the present invention has a low solid content, which effectively controls the production cost of the xBC battery, improves the printing performance, and is more conducive to the production of more complex xBC electrodes; through silver-aluminum doping, on the one hand, the cost is further reduced, and on the other hand, it can help the electrode to form a good ohmic contact with the back P area; the silver powder composition and particle size are controlled so that silver powders of different particle sizes and morphologies can fill each other, reduce resistance, and avoid shrinkage and deformation during high-temperature sintering, while also being able to control the degree of oxidation on the electrode surface to avoid affecting the conductive performance. DETAILED DESCRIPTION

[0036] The specific implementation modes of the present invention are described below by way of examples.

[0037] In a first aspect, this embodiment provides a P-region conductive paste for an xBC battery, which includes the following components:

[0038] Silver powder 83-86wt%, glass powder 3-7wt%, aluminum powder 0.5-3.5wt%, additives 0.5-3wt%, and the balance is an organic carrier;

[0039] The silver powder is a mixture of at least two of micron-sized spherical silver powder, nano-sized spherical silver powder and flaky silver powder, and the nano-sized spherical silver powder accounts for no more than 20% of the total mass of the silver powder.

[0040] Specifically, the conductive paste provided in this embodiment is doped with flaky silver powder, nano silver powder and micron silver powder. The flaky silver powder is overlapped to form a mesh frame structure. The nano silver powder and the micron silver powder fill the gaps in the frame, reducing the proportion of space inside the paste that is not filled with conductive powder, thereby reducing the resistance of the finished electrode. The frame structure filled with spherical silver powder can also improve the mechanical properties of the finished electrode. On this basis, due to the different particle sizes of the nano silver powder and the micron silver powder, the gaps can be further filled with each other, thereby further reducing the resistivity.

[0041] In a preferred implementation of this embodiment,

[0042] The silver powder is a mixture of micron-sized spherical silver powder, nano-sized spherical silver powder and flaky silver powder, wherein the mass proportion of the micron-sized spherical silver powder is 70-80%, the mass proportion of the flaky silver powder is 10-20%, and the mass proportion of the nano-sized spherical silver powder is 5-15%;

[0043] The D50 particle size of the micron-sized spherical silver powder and the flaky silver powder is 0.8 to 2.5 μm;

[0044] The particle size of the nano-scale spherical silver powder is 500-800nm.

[0045] As mentioned above, due to the different particle sizes of nano silver powder and micron silver powder, they can further fill the gaps between each other, thereby further reducing the resistivity.

[0046] In addition, since too much nano-sized silver powder will cause the slurry viscosity to be too high and cannot be printed to prepare electrodes, it is necessary to control the content of nano silver powder within a reasonable range.

[0047] In a preferred implementation of this embodiment,

[0048] The aluminum powder is specifically micron-grade spherical aluminum powder, and its D50 particle size is 0.5 to 6 μm.

[0049] In a further preferred embodiment,

[0050] The D50 particle size of the aluminum powder is 2.5 μm.

[0051] Specifically, the present embodiment uses spherical aluminum powder with a larger particle size range, which can be fully mixed, dispersed and filled with silver powder to avoid the formation of insulating voids, thereby reducing the resistivity of the finished grid electrode and improving the electrical performance; aluminum powder with a smaller particle size has a good filling and dispersion effect, and the surface oxide layer of aluminum powder with a larger particle size is easy to remove; the relatively dispersed particle size range of aluminum powder can also effectively avoid agglomeration of aluminum powder during the mixing process and cause uneven dispersion.

[0052] After many experiments by the applicant, it was determined that when the D50 particle size of aluminum powder is about 2.5 μm, a relatively ideal balance can be achieved in terms of dispersion uniformity, electrical properties and mechanical properties. Therefore, it is more preferred to choose an aluminum powder D50 particle size of 2.5 μm.

[0053] In a preferred implementation of this embodiment,

[0054] The first glass powder comprises 35-60 wt % of Bi2O3, 25-40 wt % of B2O3, and 5-20 wt % of SiO2;

[0055] The second glass powder is a mixture of at least two of BaO, ZnO, GaO, K2O, and Na2O; the mass percentage of the second glass powder is 8 to 12 wt%.

[0056] Specifically, this embodiment forms a SiO2-B2O3-Bi2O3 system by formulating glass components. The system does not contain Pb, is more environmentally friendly and safe, and has a good grid skeleton effect. On this basis, it is combined with filling of alkali metal / alkaline earth metal oxides such as BaO, ZnO, GaO, K2O, and Na2O to further improve the performance of the glass skeleton. It does not contain Al components to avoid affecting the window opening effect of the passivation layer.

[0057] In a preferred implementation of this embodiment,

[0058] The additive is a mixture of WO3, metal fluoride and silane coupling agent; based on the total mass of the additive:

[0059] The content of WO3 is 30-50wt%;

[0060] The metal fluoride content is 10-15wt%;

[0061] The content of the silane coupling agent is 30-45 wt %.

[0062] Specifically, the above-mentioned additives can firstly effectively dissolve the Ag surface oxide layer to prevent the surface oxide layer of the metal conductive powder from affecting the ohmic contact between the grid electrode and the substrate; secondly, they can modify the Al component to improve its dispersion uniformity in the slurry and avoid agglomeration, thereby ensuring electrical performance; thirdly, they can fully corrode the passivation layer of the P region of the substrate without breakdown, thereby achieving a more ideal ohmic contact.

[0063] In a preferred implementation of this embodiment, the organic carrier comprises a mixed solvent and a resin, wherein:

[0064] The mixed solvent is a mixture of terpineol and butyl carbitol and / or citric acid, and the mass proportion of the terpineol is ≥60%;

[0065] Based on the total mass of the organic carrier, the resin includes 5-8wt% of ethyl cellulose, 0-5wt% of Span series and / or Tween series, 1.5-2.5wt% of sodium dodecylbenzene sulfonate, and 0.2-0.8wt% of polyamide.

[0066] Specifically, this embodiment uses a mixture of pineol and butyl carbitol and / or citric acid as a mixed solvent. The main reason is that the solid content in the slurry provided in this embodiment is relatively low. According to the applicant's test, the volatility of the above mixture is relatively ideal at low and high temperatures, which is conducive to the printing and sintering of low-solid slurry.

[0067] In a second aspect, this embodiment provides a method for preparing the conductive paste, comprising the following steps:

[0068] S1, dispersing and mixing the silver powder and the additive uniformly, then adding the aluminum powder, dispersing and mixing uniformly to obtain a first product;

[0069] S2, mixing the glass powder and the organic carrier uniformly to obtain a second product;

[0070] S3. Mix the first product and the second product, and stir them thoroughly to obtain the conductive paste.

[0071] In a third aspect, this embodiment provides an xBC battery back P region electrode, specifically, the electrode is prepared by using the above conductive paste through a metallization process. The metallization process includes screen printing and high temperature sintering.

[0072] In a fourth aspect, this embodiment provides an xBC battery, wherein the P-region electrode thereof adopts the above-mentioned electrode.

[0073] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0074] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A P-zone conductive paste for xBC battery, characterized in that: It is composed of the following components: Silver powder 83~86wt%, glass powder 3~7wt%, aluminum powder 0.5~3.5wt%, additives 0.5~3wt%, and the balance is organic carrier; The silver powder is a mixture of micron-sized spherical silver powder, nano-sized spherical silver powder and flaky silver powder, wherein the mass proportion of the micron-sized spherical silver powder is 70-80%, the mass proportion of the flaky silver powder is 10-20%, and the mass proportion of the nano-sized spherical silver powder is 5-15%; the D50 particle sizes of the micron-sized spherical silver powder and the flaky silver powder are both 0.8-2.5 μm; the particle size of the nano-sized spherical silver powder is 500-800 nm; The aluminum powder is specifically micron-sized spherical aluminum powder, and its D50 particle size is 0.5-6 μm; The additive is a mixture of WO3, metal fluoride and silane coupling agent; based on the total mass of the additive: The content of WO3 is 30-50wt%; The metal fluoride content is 10-15wt%; The content of the silane coupling agent is 30-45wt%.

2. The conductive paste according to claim 1, characterized in that: The D50 particle size of the aluminum powder is 2.5 μm.

3. The conductive paste according to claim 1, characterized in that: The organic carrier includes a mixed solvent and a resin; The mixed solvent is a mixture of terpineol and butyl carbitol and / or citric acid, and the mass proportion of the terpineol is ≥60%; Based on the total mass of the organic carrier, the resin includes 5-8wt% of ethyl cellulose, 0-5wt% of Span series and / or Tween series, 1.5-2.5wt% of sodium dodecylbenzene sulfonate, and 0.2-0.8wt% of polyamide.

4. The method for preparing the conductive paste according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, dispersing and mixing the silver powder and the additive uniformly, then adding the aluminum powder, dispersing and mixing uniformly to obtain a first product; S2, mixing the glass powder and the organic carrier uniformly to obtain a second product; S3. Mix the first product and the second product, and stir them thoroughly to obtain the conductive paste.

5. A P-region electrode on the back side of an xBC battery, characterized in that: The conductive paste according to any one of claims 1 to 3 is prepared by a metallization process.

6. An xBC battery, characterized in that: The P-region electrode adopts the electrode described in claim 5.