Disclosure of Invention
Aiming at the prior art, the invention provides the conductive paste for the front electrode of the solar cell, which adopts glass powder with different glass transition temperatures as an inorganic adhesive of the conductive paste, and improves the conversion efficiency and the tensile force of the solar cell.
The invention also provides a preparation method of the conductive paste for the front electrode of the solar cell aiming at the prior art.
The invention also provides a front electrode of the solar cell, which applies the conductive slurry adopting the glass powder with different glass transition temperatures as the inorganic adhesive on the silicon chip, improves the printing performance of the front electrode of the solar cell and reduces the unit consumption.
The invention is realized by the following technical scheme: the conductive paste for the solar cell front electrode is added with 1.7-4% by mass of glass powder A and 0.1-1% by mass of glass powder B; the glass transition temperature of the glass powder A is 250-350 ℃, and preferably 260-300 ℃; the glass transition temperature of the glass powder B is 350-450 ℃, and preferably 370-420 ℃.
In the technical scheme, the glass transition temperatures of the glass powder A and the glass powder B have a temperature difference, preferably, the temperature difference is preferably 70-150 ℃.
In the technical scheme, because the glass transition temperature between the glass powder A and the glass powder B has temperature difference, in the sintering process of sintering the conductive silver paste, the glass powder A with lower glass transition temperature is firstly softened and melted, the fluidity is enhanced, the silver powder in the conductive paste is carried to the surface of the silicon wafer, and the surface of the silicon wafer is etched; along with the continuous rise of the sintering temperature, the glass powder B with higher glass transition temperature is softened and melted, the surface of the silicon chip is further etched, the etching degree of the surface of the silicon chip is higher,
further, the glass powder A is TeO2-PbO-Bi2O3-SiO2A glass powder system; the glass powder B is TeO2-Bi2O3-WO3-MgO-SiO2The system is glass powder.
Further, the TeO2-PbO-Bi2O3-SiO2The system glass powder comprises the following components in parts by mass: 25-45 parts of TeO215-30 parts of PbO and 17-32 parts of Bi2O31 to 10 parts of SiO2。
Further, the TeO2-PbO-Bi2O3-SiO2Trace additives are also added into the system glass powder; the mass portion of the trace additive is 0.1-15.
Further, the micro additive is WO3、ZnO、Al2O3、B2O3、CaO、Na2O, MgO, respectively. Preferably, the micro additive comprises WO3、ZnO、Al2O3、B2O3、CaO、Na2O、MgO。
Further, the TeO2-Bi2O3-WO3-MgO-SiO2The system glass powder comprises the following components in parts by mass: 8-15 parts of TeO250 to 70 parts of Bi2O310 to 20 portions of WO35 to 10 parts of MgO, 1 to 3 parts of SiO2。
Further, the TeO2-Bi2O3-WO3-MgO-SiO2A trace amount of inorganic oxide is also added into the system glass powder; the mass portion of the trace inorganic oxide is 0.1-15.
Further, the trace inorganic oxide is Al2O3、Li2O、Na2One or more of O. Preferably, the trace inorganic oxide comprises Al2O3、Li2O、Na2O。
Further, the conductive paste also comprises the following components in percentage by mass: 85-92% of spherical silver powder, 1.5-6% of organic carrier, 2-5% of diluent and 1.0-2.0% of auxiliary agent.
Furthermore, D50 of the glass powder A and the glass powder B is 0.5-2.2 μm, preferably 0.8-2.0 μm, more preferably 1.4-1.8 μm, and D100 is not more than 6.0 μm.
Further, the organic carrier comprises the following components in parts by weight: 6-10 parts of ethyl cellulose resin, 2-5 parts of acrylic resin, 1-4 parts of PVB resin and 86-90 parts of solvent. Wherein the solvent is one or more of butyl carbitol acetate, butyl carbitol and alcohol ester dodeca, and the function of the solvent is to adjust the viscosity and the solubility of the organic carrier.
Further, the diluent is one or more of butyl carbitol acetate, butyl carbitol, alcohol ester dodeca and DBE-3.
Further, the auxiliary agent is preferably silicone oil, a thixotropic agent and a dispersing agent. Wherein the silicone oil can be selected from silicone oil with the viscosity of 1000-5000 cst; the thixotropic agent is preferably Thixatrol ST and MT, either alone or in admixture; the non-dispersant is preferably one or more of OP-83RAT, 1561 and ED-350.
The invention also discloses a preparation method of the conductive paste for the front electrode of the solar cell, which comprises the following steps:
preparing glass powder A and glass powder B: mixing the components of the glass powder A according to a formula, and then carrying out hot melting, cooling, ball milling and sieving to obtain the glass powder A; mixing the components for forming the glass powder B according to a formula, and then carrying out hot melting, cooling, ball milling and sieving to obtain glass powder B;
preparing an organic carrier: adding the resin into a solvent, preserving the heat for 1-3 hours at the temperature of 70-90 ℃, and filtering to obtain an organic carrier;
preparing conductive slurry: adding the glass powder A and the glass powder B into the organic carrier, adding other components of the conductive paste, mixing and dispersing until the particle size of the particulate matter is not more than 7 mu m, and filtering to obtain the conductive paste.
The invention also discloses application of the conductive paste to a front electrode of a solar cell, and particularly discloses a front electrode which is formed by printing conductive silver paste on a silicon chip of the solar cell in a silk screen manner by a silk screen printing technology and sintering the conductive silver paste at the temperature of 500-900 ℃.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) according to the conductive paste for the front electrode of the solar cell, provided by the invention, the glass powder A and the glass powder B with different glass state softening temperatures are used as inorganic adhesives of the conductive paste, so that the adhesive property of the conductive paste on the surface of a silicon wafer is improved, the degree of etching the surface of the silicon wafer by molten glass powder in the conductive paste is improved, the doping is improved, the smaller the ohmic contact of a metal-semiconductor contact layer on the surface of the silicon wafer is, and the unit consumption ratio of the front electrode of the solar cell is reduced by 5-10%.
(2) According to the conductive paste for the front electrode of the solar cell, provided by the invention, the ethyl cellulose carrier is added to improve the printability and sintering temperature of the conductive silver paste, so that the grid line printed by the conductive silver paste is not easy to have the problems of grid breakage, virtual printing and the like; the viscosity of the conductive paste is adjusted by adjusting the proportion of the components in the organic carrier, so that the conductive paste has good printing lines, and the phenomenon of poor printing in the printing process is avoided; and the weight ratio relationship between the glass powder system and the spherical silver powder is adjusted, so that the requirement of the current diamond wire cutting battery piece is met.
(3) According to the preparation method of the conductive paste for the front electrode of the solar cell, disclosed by the invention, the glass powder A and the glass powder B with different glass state softening temperatures are added into the conductive paste, so that the conductive paste with low contact resistance, higher cell conversion rate and good printing performance is obtained.
(4) According to the solar cell front electrode disclosed by the invention, the silver conductive grid line is printed by adopting the conductive slurry added with the glass powder A and the glass powder B with different glass transition temperatures as inorganic adhesives and is sintered into the solar cell front electrode, the conversion rate of the front electrode is higher, the contact resistance is low, and the single consumption is reduced by 5-10% compared with that of the conventional solar cell.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
In the prior art, after the diamond wire is used for cutting, the surface of a battery piece is smoother, the surface of a cut silicon wafer has obvious cutting lines, and the traditional slurry is used, so that the requirements on tension and printability cannot be met.
Based on the problems, the application discloses conductive paste for a front electrode of a solar cell, which comprises 85-92% of spherical silver powder, 1.5-6% of organic carrier, 2-5% of diluent, 1.0-2.0% of auxiliary agent, 1.7-4% of glass powder A and 0.1-1% of glass powder B by mass; the glass transition temperature of the glass powder A is 250-350 ℃, and preferably 260-300 ℃; the glass transition temperature of the glass powder B is 350-450 ℃, and preferably 370-420 ℃.
In some embodiments, the glass frit A is TeO2-PbO-Bi2O3-SiO2A glass powder system; the glass powder B is TeO2-Bi2O3-WO3-MgO-SiO2The system is glass powder.
In some embodiments, the TeO2-PbO-Bi2O3-SiO2The system glass powder comprises the following components in parts by mass: 25-45 parts of TeO215-30 parts of PbO and 17-32 parts of Bi2O31 to 10 parts of SiO2。
In some embodiments, the TeO2-PbO-Bi2O3-SiO2Trace additives are also added into the system glass powder; the mass portion of the trace additive is 0.1-15.
In some embodiments, the micro-additive is WO3、ZnO、Al2O3、B2O3、CaO、Na2O, MgO, respectively. Preferably, the micro additive comprises WO3、ZnO、Al2O3、B2O3、CaO、Na2O、MgO。
In some embodiments, the TeO2-Bi2O3-WO3-MgO-SiO2The system glass powder comprises the following components in parts by mass: 8-15 parts of TeO250 to 70 parts of Bi2O310 to 20 portions of WO35 to 10 parts of MgO, 1 to 3 parts of SiO2。
In some embodiments, the TeO2-Bi2O3-WO3-MgO-SiO2A trace amount of inorganic oxide is also added into the system glass powder; the mass portion of the trace inorganic oxide is 0.1-15.
In some embodiments, the trace inorganic oxide is Al2O3、Li2O、Na2One or more of O. Preferably, the trace inorganic oxide comprises Al2O3、Li2O、Na2O。
In some embodiments, D50 of the glass powder A and the glass powder B is 0.5-2.2 μm, preferably 0.8-2.0 μm, more preferably 1.4-1.8 μm, and D100 is not more than 6.0 μm.
In some embodiments, the organic vehicle comprises the following ingredients, listed in parts by weight: 6-10 parts of ethyl cellulose resin, 2-5 parts of acrylic resin, 1-4 parts of PVB resin and 86-90 parts of solvent. Wherein the solvent is one or more of butyl carbitol acetate, butyl carbitol and alcohol ester dodeca, and the function of the solvent is to adjust the viscosity and the solubility of the organic carrier.
In some embodiments, the diluent is one or more of butyl carbitol acetate, butyl carbitol, alcohol ester dodeca, DBE-3.
In some embodiments, the adjuvant is preferably a silicone oil, a thixotropic agent, and a dispersing agent. Wherein the silicone oil can be selected from silicone oil with the viscosity of 1000-5000 cst; the thixotropic agent is preferably Thixatrol ST and MT, either alone or in admixture; the non-dispersant is preferably one or more of OP-83RAT, 1561 and ED-350.
The conductive paste for the front electrode of the solar cell disclosed in the present document can be prepared by the following method:
A1) preparing glass powder A and glass powder B: mixing the components of the glass powder A according to a formula, and then carrying out hot melting, cooling, ball milling and sieving to obtain the glass powder A; mixing the components for forming the glass powder B according to a formula, and then carrying out hot melting, cooling, ball milling and sieving to obtain glass powder B;
A2) preparing an organic carrier: adding the resin into a solvent, preserving the heat for 1-3 hours at the temperature of 70-90 ℃, and filtering to obtain an organic carrier;
A3) preparing conductive slurry: adding the glass powder A and the glass powder B into the organic carrier, adding other components of the conductive paste, mixing and dispersing until the particle size of the particulate matter is not more than 7 mu m, and filtering to obtain the conductive paste.
The conductive paste for the front electrode of the solar cell disclosed in the present application can be applied to the solar cell in the following manner
The invention is further illustrated by the following specific application examples:
example 1
The conductive paste used in this example was formulated as follows: 1.7 percent of glass powder A, 1 percent of glass powder B, 90 percent of spherical silver powder, 2.2 percent of organic carrier, 3.65 percent of diluent and 1.45 percent of auxiliary agent, and the specific formula components are shown in Table 1.
The preparation method specifically comprises the following steps:
A1) preparing glass powder A and glass powder B:
A11) according to the raw materials and the proportion shown in Table 1, TeO is added2、PbO、Bi2O3、SiO2、WO3、ZnO、Al2O3、B2O3、CaO、Na2And mixing O and MgO uniformly, heating, then carrying out hot melting, cooling, ball milling and sieving to obtain glass powder A, wherein D50 of the glass powder is preferably 1.8 mu m.
A12) According to the raw materials and the proportion shown in Table 1, TeO is added2、Bi2O3、WO3、MgO、SiO2、Al2O3、Li2O、Na2And O is uniformly mixed, heated, melted, cooled, ball-milled and sieved to obtain the glass powder B, wherein D50 of the glass powder is preferably 1.6 mu m.
A2) Preparing an organic carrier:
adding ethyl cellulose resin, acrylic resin and PVB resin into a solvent according to the raw materials and the proportion shown in the table 1, completely dissolving the ethyl cellulose resin, the acrylic resin and the PVB resin at the constant temperature of 80 ℃, preserving the temperature for 2 hours, and filtering the mixture by using a 250-mesh standard sieve to obtain the organic carrier.
A3) Preparing conductive slurry:
uniformly mixing the glass powder prepared in the step A1), the organic carrier prepared in the step A2), the spherical silver powder, the diluent and the auxiliary agent according to the raw materials and the proportion shown in the table 1, dispersing the mixture on a three-roll machine to be less than 7 microns, adjusting the mixture to be proper in viscosity, and filtering the mixture to obtain the conductive paste for the front electrode of the solar cell.
Example 2
The conductive paste used in this example was formulated as follows: the glass powder comprises 2% of glass powder A, 0.2% of glass powder B, 92% of spherical silver powder, 1.5% of organic carrier, 3% of diluent and 1.3% of auxiliary agent, and the specific formula components are shown in Table 1. The preparation method is basically the same as that of example 1, and therefore, detailed description is omitted.
Example 3
The conductive paste used in this example was formulated as follows: 2.1 percent of glass powder A, 0.5 percent of glass powder B, 85 percent of spherical silver powder, 6 percent of organic carrier, 4.85 percent of diluent and 1.55 percent of auxiliary agent, and the specific formula components are shown in Table 1. The preparation method is basically the same as that of example 1, and therefore, detailed description is omitted.
Example 4
The conductive paste used in this example was formulated as follows: the glass powder comprises 1.8% of glass powder A, 0.4% of glass powder B, 87% of spherical silver powder, 4.6% of organic carrier, 4.55% of diluent and 1.65% of auxiliary agent, and the specific formula components are shown in Table 1. The preparation method is basically the same as that of example 1, and therefore, detailed description is omitted.
Example 5
The conductive paste used in this example was formulated as follows: 2.5 percent of glass powder A, 0.45 percent of glass powder B, 88 percent of spherical silver powder, 3.5 percent of organic carrier, 3.85 percent of diluent and 1.7 percent of auxiliary agent, and the specific formula components are shown in Table 1. The preparation method is basically the same as that of example 1, and therefore, detailed description is omitted.
TABLE 1
Printing the conductive paste prepared in the above embodiments 1 to 5 on the front electrode of the solar cell of the diamond wire-cut silicon wafer by using a non-mesh screen with a fine grid line width of 24 μm, and sintering at a sintering temperature of: room temperature → 300 ℃ → 360 ℃ → 520 ℃ → 540 ℃ → 640 ℃ → 820 ℃ → room temperature.
Tensile force, unit consumption and photoelectric conversion efficiency performance detection are carried out on the sintered solar cell front electrode, and the detection results are shown in table 2:
|
example 1
|
Example 2
|
Example 3
|
Example 4
|
Example 5
|
Aspect ratio
|
0.4632
|
0.4452
|
0.4562
|
0.4485
|
0.4535
|
Pulling force (N)
|
2.7
|
3.5
|
2.6
|
2.8
|
3.0
|
Unit consumption (g)
|
0.0785
|
0.0772
|
0.0788
|
0.0754
|
0.0763
|
Photoelectric conversion efficiency Eff (%)
|
18.94
|
18.97
|
19.12
|
19.21
|
19.02 |
TABLE 2
As shown in table 2, when the conductive paste disclosed in this document is applied to the front electrode of the solar cell, the photoelectric conversion rate is high, the unit consumption is low, and the adhesion performance is good.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.