KR20190058113A - Glass frit, paste for forming perc solar cell electrode comprising the same and perc solar cell electrode - Google Patents

Abstract

The present invention relates to a glass frit having excellent electrical properties, a paste for forming a PERC solar cell electrode including the same, and a PERC solar cell electrode thereof. The glass frit of the present invention comprises 0.5 to 5 mol% of gallium oxide (Ga_2O_3), and further comprises at least one or more from silicon oxide (SiO_2), lithium oxide (Li_2O), lead oxide (PbO), and tellurium oxide (TeO_2).

Description

[0001] The present invention relates to a glass frit, a paste for forming a PERC solar cell electrode including the same, and a paste for a PERC solar cell electrode,

The present invention relates to glass frit, a paste for forming a PERC solar cell electrode comprising the same, and a PERC solar cell electrode.

A solar cell is a device that separates incident photons into electrons and holes through a photoelectric effect and collects them through pn junctions to generate electricity. The front and rear electrodes are formed on the upper and lower surfaces of the solar cell, respectively, and the electrode of the solar cell can be formed by applying, patterning and firing a paste for forming a solar cell electrode.

As the paste for forming a solar cell electrode, a paste containing conductive powder, glass frit, and organic vehicle is used. Among them, the glass frit dissolves the antireflection film formed on the semiconductor wafer to make the conductive powder come into electrical contact with the semiconductor substrate. Particularly, the glass frit plays an important role, And the conversion efficiency of the solar cell can be changed accordingly.

Meanwhile, attention has been paid to a PERC solar cell having a passivation layer to prevent the recombination of electrons and holes generated in a back electrode in a solar cell and disappearing. However, the passivation layer is damaged by the high temperature of the firing process, thereby deteriorating the performance of the solar cell.

Therefore, it is necessary to develop a paste for forming a solar cell electrode having a low firing temperature in order to apply it to an electrode of a PERC solar cell as well as an excellent electrical characteristic.

Prior art related to this is disclosed in Korean Patent No. 10-0846306.

It is an object of the present invention to provide a glass frit having excellent electrical characteristics at a low firing temperature, a paste for forming a PERC solar cell electrode comprising the same, and a PERC solar cell electrode.

Another object of the present invention is to provide glass frit having a low series resistance, excellent fill factor and conversion efficiency, a paste for forming a PERC solar cell electrode comprising the same, and a PERC solar cell electrode.

The above and other objects of the present invention can be achieved by the present invention described below.

One aspect of the invention relates to glass frit.

According to one embodiment, the glass frit comprises gallium oxide (Ga ₂ O ₃₎ 0.5 to 5 mol%.

The glass frit may further include at least one of silicon oxide (SiO ₂ ), lithium oxide (Li ₂ O), lead oxide (PbO), and tellurium oxide (TeO ₂ ).

Wherein the glass frit comprises 6 to 19 mol% lead oxide, 1 to 10 mol% bismuth oxide, 11 to 24 mol% tellurium oxide, 31 to 44 mol% silicon oxide, 1 to 9 mol% zinc oxide, Mol%, tungsten oxide 1 to 9 mol%, and gallium oxide 0.5 to 5 mol%.

The glass frit may have a molar ratio of gallium oxide (Ga ₂ O ₃ ) and lead oxide (PbO) of 0.2: 1 to 1: 1.

The glass frit may have a molar ratio of gallium oxide (Ga ₂ O ₃ ) and tellurium oxide (TeO ₂ ) of 0.15: 1 to 1: 1.

The glass frit may have a total content of silicon oxide (SiO ₂ ) and lithium oxide (Li ₂ O) of 50 mol% to 80 mol%.

The glass frit may have a total content of lead oxide (PbO) and tellurium oxide (TeO ₂ ) of 20 mol% to 35 mol%.

The glass frit may further comprise at least one of bismuth oxide (Bi ₂ O ₃ ), zinc oxide (ZnO) and tungsten oxide (WO ₃ ).

The glass frit may be made of at least one selected from the group consisting of Bi, Zn, Na, Tl, P, Ge, Ce, (Mg), molybdenum (Mo), cesium (Cs), strontium (Sr), titanium (Ti), tin (Sn), indium (In), vanadium (V), barium (Ba) At least one metal oxide selected from the group consisting of copper (Cu), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and aluminum (Al).

Another aspect of the present invention relates to a paste for forming a PERC solar cell electrode.

In one embodiment, the PERC solar cell electrode-forming paste may comprise the above glass frit, conductive powder, and organic vehicle.

The paste may have a firing temperature of 700 ° C to 800 ° C.

The paste may include 750 to 95 wt% of the conductive powder, 0.1 to 10 wt% of the glass frit, and 3 to 20 wt% of the organic vehicle.

The paste may further include at least one of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, a defoamer, a pigment, a UV stabilizer, an antioxidant and a coupling agent.

The PERC solar cell electrode, which is another aspect of the present invention, can be made of the paste for forming the PERC solar cell electrode.

The present invention provides a glass frit having excellent electrical characteristics even at a low firing temperature, low in series resistance, excellent in fill factor and conversion efficiency, a paste for forming a PERC solar cell electrode containing the glass frit, and a PERC solar cell electrode .

FIG. 1 is a schematic view of a structure of a PERC solar cell according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

In the following description of the present invention, detailed description of known related arts will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured by the present invention.

In the case where the word 'includes', 'having', 'done', etc. are used in this specification, other parts can be added unless '~ only' is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

Also, in interpreting the constituent elements, even if there is no separate description, it is interpreted as including the error range.

In this specification, 'metal oxide' may mean one metal oxide and may refer to a plurality of metal oxides.

In this specification, 'glass frit' may include at least one of a glass phase and a crystal phase, and may be a glass ceramic.

In the present specification, 'X to Y' representing the range means 'X or more and Y or less'.

Glass frit

The glass frit acts to form contact between the electrode and the emitter by the process of melting the conductive powder, etching the antireflection film, and re-precipitating the conductive powder in the firing process during the electrode formation process. The glass frit can be used for a paste for forming a solar cell electrode, particularly a paste for forming a PERC solar cell electrode.

The glass frit of the present invention may be formed from a metal oxide. The glass frit comprises 0.5 to 5 mol%, specifically 1 to 4.5 mol%, more particularly 1.7 to 4 mol% of gallium oxide (Ga ₂ O ₃ ). In the above range of mol%, the firing temperature of the glass frit-containing paste is low, so that it is suitable for forming a PERC solar cell electrode and has excellent balance of electrical characteristics.

Specifically, the glass frit may be formed from a metal oxide, for example, a metal oxide may be mixed using a ball mill or a planetary mill, Is melted at a temperature of 900 ° C to 1300 ° C, cooled with a shaking roller to produce a cullet shape, and then pulverized by a disk mill, a planetary mill or the like. The glass frit may have an average particle diameter (D50) of 0.1 占 퐉 to 10 占 퐉.

The glass frit has a molar ratio of gallium oxide (Ga ₂ O ₃ ) and lead oxide (PbO) of 0.2: 1 to 5: 1, specifically 0.2: 1 to 1: 1, more specifically 0.2: Lt; / RTI > There is an advantage in that the contact resistance and conversion efficiency of the electrode are excellent in the above-mentioned mole ratio range.

The glass frit has a molar ratio of gallium oxide (Ga ₂ O ₃ ) and tellurium oxide (TeO ₂ ) of 0.15: 1 to 3: 1, specifically 0.15: 1 to 1: 1, more specifically 0.15: 1 < / RTI > The series resistance and the fill factor of the electrode are excellent in the above-mentioned molar ratio range.

The glass frit may have a total content of silicon oxide (SiO ₂ ) and lithium oxide (Li ₂ O) of 50 mol% to 80 mol%, specifically 52 mol% to 75 mol%. The contact resistance of the electrode is low in the above content range.

The glass frit may have a total content of lead oxide (PbO) and tellurium oxide (TeO ₂ ) of 20 mol% to 35 mol%. The shunt resistance of the electrode can be lowered in the above content range.

The glass frit may have a molar content of silicon oxide greater than the sum of the molar content of lead oxide and tellurium oxide. In the above content range, the fill factor and conversion efficiency of the electrode are excellent.

The glass frit may further comprise at least one of bismuth oxide (Bi ₂ O ₃ ), zinc oxide (ZnO) and tungsten oxide (WO ₃ ). In this case, since the firing temperature of the glass frit-containing paste is low, it is suitable for forming the electrode of the PERC solar cell, and the balance of the electrical characteristics of the electrode can be controlled optimally.

The glass frit may be made of at least one selected from the group consisting of Bi, Zn, Na, Tl, P, Ge, Ce, (Mg), molybdenum (Mo), cesium (Cs), strontium (Sr), titanium (Ti), tin (Sn), indium (In), vanadium (V), barium (Ba) At least one metal oxide selected from the group consisting of copper (Cu), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and aluminum (Al).

In an embodiment, the glass frit comprises 6 to 19 mole percent lead oxide, 1 to 10 mole percent bismuth oxide, 11 to 24 mole percent tellurium oxide, 31 to 44 mole percent silicon oxide, 1 to 9 mole percent zinc oxide, 16 to 24 mol% of the oxide, 1 to 9 mol% of the tungsten oxide and 0.5 to 5 mol% of the gallium oxide. In the above range, the firing temperature of the glass frit-containing paste is low, so that it is suitable for forming electrodes of PERC solar cells, has a low series resistance of electrodes, and is excellent in conversion efficiency of solar cells.

PERC  For forming solar cell electrodes Paste

The paste for forming a PERC solar cell electrode of the present invention may include a glass frit, a conductive powder, and an organic vehicle according to one aspect of the present invention.

Hereinafter, each component of the paste of the present invention will be described in detail.

Glass frit

The glass frit may be substantially the same as the glass frit according to one aspect of the present invention.

The glass frit may be contained in the paste for forming the PERC solar cell electrode in an amount of 0.1 to 10% by weight, specifically 0.5 to 5% by weight. In the above content range, the contactability between the electrode and the emitter is excellent, the pn junction stability can be ensured, and the efficiency of the solar cell can be improved by minimizing the resistance.

Conductive powder

The conductive powder may be a metal powder such as silver (Ag) or aluminum (Al). For example, silver powder may be used. The conductive powder may be a powder having a nano-sized or micro-sized particle size, for example, 3 탆 to 15 탆, specifically, 5 탆 to 11 탆. It is possible to reduce the resistance in the above range and to prevent cracking of the electrode.

In addition, silver powder having two or more different sizes may be mixed with the conductive powder.

The shape of the conductive powder is not particularly limited, and particles having various shapes, for example, spherical, plate-like or amorphous shapes may be used without limitation.

The conductive powder may be an electrically conductive metal other than silver. Specifically, copper, gold, silver, palladium, platinum, mixtures thereof, and alloys thereof can be used.

The conductive powder may include 75 to 95% by weight, specifically 78 to 93% by weight of the paste for forming the PERC solar cell electrode. In the above content range, the conversion efficiency of the PERC solar cell is excellent, and the paste can be smoothly formed.

abandonment Vehicle

The organic vehicle can impart an appropriate viscosity to the paste for forming the PERC solar cell electrode and serves to improve the fairness.

The organic vehicle may be an organic vehicle ordinarily used in a paste for forming a solar cell electrode, and may include, for example, a binder resin and a solvent.

As the binder resin, an acrylate-based or cellulose-based resin can be used, and ethylcellulose is generally used. However, it is preferable to use a mixture of ethylhydroxyethylcellulose, nitrocellulose, a mixture of ethylcellulose and phenol resin, an alkyd resin, a phenol resin, an acrylic ester resin, a xylene resin, a polybutene resin, a polyester resin, Based resin, a rosin of wood, or a polymethacrylate of alcohol may be used.

Examples of the solvent include hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl carbitol (diethylene glycol monobutyl ether), dibutyl carbitol (diethylene glycol dibutyl ether) , Butyl carbitol acetate (diethylene glycol monobutyl ether acetate), propylene glycol monomethyl ether, hexylene glycol, terpineol, methyl ethyl ketone, benzyl alcohol, gamma butyrolactone or ethyl lactate, Texanol) may be used singly or in combination of two or more.

The organic vehicle may include 3 to 20% by weight of the paste for forming a PERC solar cell electrode. Sufficient adhesive strength and excellent printability can be ensured in the above content range.

additive

The paste for forming a PERC solar cell electrode of the present invention may further include conventional additives as needed in order to improve flow characteristics, process characteristics, and stability in addition to the above components. The additive may be used alone or as a mixture of two or more of a dispersing agent, a thixotropic agent, a plasticizer, a viscosity stabilizer, a defoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant and a coupling agent. These may be contained in an amount of 0.1 to 5% by weight based on the total weight of the paste for forming a PERC solar cell electrode, but the content can be changed as necessary.

The paste for forming the PERC solar cell electrode may have a firing temperature of 700 ° C to 800 ° C, specifically 750 ° C to 795 ° C. In the firing temperature range, it is suitable for use in a PERC solar cell electrode, and in particular, it is possible to minimize the damage of the passivation layer, thereby improving the efficiency of the PERC solar cell.

PERC  Solar cell electrodes and PERC  Solar cell

Another aspect of the present invention relates to an electrode formed from the paste for forming the PERC solar cell electrode and a PERC solar cell including the same. 1 shows a structure of a PERC solar cell according to an embodiment of the present invention.

1, a PERC solar cell 100 according to an embodiment of the present invention includes substrates 20 and 30, a front electrode 10 formed on the front surfaces of the substrates 20 and 30, And a back electrode 50 formed on the passivation layer 40. The passivation layer 40 is formed on the rear surface of the passivation layer 40,

In one embodiment, the substrate may be a substrate on which a PN junction is formed. Specifically, the substrate may include a semiconductor substrate 30 and an emitter 20. More specifically, the substrate may be a substrate on which an N-type emitter 20 is formed by doping an N-type dopant on one surface of the P-type semiconductor substrate 30. Alternatively, the substrate may be a substrate on which the P-type emitter 20 is formed by doping a P-type dopant on one surface of the N-type semiconductor substrate 30. At this time, the semiconductor substrate 30 means either a P-type substrate or an N-type substrate. The P-type substrate may be a semiconductor substrate 11 doped with a P-type dopant, and the N-type substrate may be a semiconductor substrate 11 doped with an N-type dopant.

For example, the semiconductor substrate 30 may be made of crystalline silicon or a compound semiconductor. At this time, the crystalline silicon may be single crystalline or polycrystalline. As the crystalline silicon, for example, a silicon wafer can be used. In this case, the P-type dopant may be a material containing Group III elements of the periodic table such as boron, aluminum, and gallium. In addition, the N-type dopant may be a material containing elements in the group V of the periodic table such as phosphorus, arsenic, and antimony.

The front electrode 10 and / or the rear electrode 50 may be manufactured using the electrode forming paste according to the present invention. Specifically, the front electrode 10 may be manufactured using a paste using silver powder as the conductive powder, and the back electrode 50 may be manufactured using a paste using aluminum powder as the conductive powder. The front electrode 10 may be formed by printing and firing an electrode forming paste on the emitter 20 and the rear electrode 50 may be formed by a passivation layer 40 formed on the rear surface of the semiconductor substrate 11 ), And then firing the paste.

The PERC solar cell 100 includes a passivation layer 40 between a semiconductor substrate 30 and a back electrode 50. The passivation layer prevents the recombination of electrons and holes generated in the back electrode of the solar cell to disappear, thereby further improving the PERC solar cell efficiency. The rear electrode 50 may be electrically connected to the semiconductor substrate 30 through a hole formed in at least a portion of the passivation layer 40.

The PERC solar cell 100 may further include an antireflection film (not shown) on the emitter 20. The antireflection film minimizes the sunlight that is not converted into electricity by reflection in the PERC solar cell, thereby further improving the efficiency of the PERC solar cell. The texturing process may be performed before forming the antireflection film. In this case, the light reflection of the solar cell may be reduced to further improve the PERC solar cell conversion efficiency.

In addition, the PERC solar cell 100 may further include a capping layer (not shown) between the passivation layer 40 and the back electrode 50. The capping layer has the effect of improving the conversion efficiency by retroreflecting long wavelength solar light and protecting the passivation layer from the back electrode (e.g., aluminum back electrode), thereby improving the conversion efficiency of the PERC solar cell.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example  One

As an organic binder, 0.5 wt% of ethyl cellulose (DOW CHEMICAL, ETOCHEL) was dissolved in 7.5 wt% of butylcarbitol acetate as a solvent at 50 ° C, and a spherical silver powder having an average particle diameter of 2 μm (BYK-102, manufactured by BYK Co., Ltd., trade name, manufactured by BYK Co., Ltd.) as an additive, 0.5% by weight of an antiseptic agent (Cray Vallay, Cray Vallac MT), 89% by weight of a glass frit having an average particle size of 2 μm ), And the mixture was evenly mixed and dispersed with a 3-roll mill to prepare a paste for forming a PERC solar cell electrode.

Example  2 to 23 and a comparison of 1 to 2

A paste for forming a PERC solar cell electrode was prepared in the same manner as in Example 1, except that the glass frit was applied as shown in Table 1 below.

How to measure property

(1) Firing temperature (占 폚): The firing temperature of the belt firing furnace for firing the PERC solar cell electrode-forming paste prepared in Examples and Comparative Examples was measured by placing a temperature measuring sensor (DATAPAQ, Q-18) The actual temperature profile of the wafer is measured, and the temperature corresponding to the peak is shown in Table 2.

(2) Glass meltability: The batches were mixed in the platinum crucibles in the composition ratios of the metal oxides of the examples and the comparative examples and held for 20 minutes in a 1250 占 폚 melting furnace to observe the state of the melt after melting. The state of the wave glass was observed and evaluated according to the following criteria.

◎: Completely melted and vitrified upon cooling

?: Completely melted or crystallized during cooling

?: Phase separation (molten glass + solid phase precipitation) in the molten glass

X: Unmelted material remains in the molten glass

(3) Contact Resistance (Rc, m? · Cm ² ): The PERC solar cell electrode-forming paste prepared in the above Examples and Comparative Examples was screen-printed on the front surface of the wafer in a pattern for measurement of a TLM , And dried using an infrared drying furnace. The cell formed by the above process was fired at a peak temperature of 780 ° C. to 790 ° C. using a belt type firing furnace. The contact resistance (Rc, mΩ · cm ² ) of the solar cell was measured using the probe station And is shown in Table 2.

(4) The series resistance (Rs,?), The shunt resistance (Rsh,?), The short circuit current (Isc, A), the open voltage (Voc, V), the fill factor (%) and the efficiency The paste for forming a PERC solar cell electrode prepared in Comparative Example was screen-printed on the entire surface of the wafer in a predetermined pattern, and dried using an infrared drying furnace. Thereafter, aluminum paste was printed on the rear side of the wafer and then dried in the same manner. The cells thus formed were fired at a peak temperature of 780 ° C. to 790 ° C. using a belt-type firing furnace. The cells thus manufactured were connected in series with a solar cell using a solar cell efficiency measuring device (Wavelabs, SINUS-220) Table 2 shows the resistance (Rs, Ω), shunt resistance (Rsh, Ω), short circuit current (Isc, A), open voltage (Voc, V), fill factor (%) and efficiency (%

As shown in Table 2, the paste for forming a PERC solar cell electrode in which the content of silicon oxide and lithium oxide of the glass frit is in the scope of the present invention is excellent in all electrical characteristics by firing between 780 ° C and 790 ° C, It can be seen that it is suitable for application to electrode formation.

On the other hand, in Comparative Examples 1 and 2 which do not contain gallium oxide or exceed the scope of the present invention, when the low-temperature baking (780 ° C to 790 ° C), the contact resistance is high and the fill factor and conversion efficiency And it is not suitable for forming a PERC solar cell electrode.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are in all respects illustrative and not restrictive.

10: front electrode
20: Emitter
30: semiconductor substrate
40: Passivation layer
50: rear electrode
100: PERC solar cell

Claims (14)

Gallium oxide (Ga ₂ O ₃₎ glass frit containing 0.5 to 5 mol%.
The method according to claim 1,
The glass frit is glass frit further comprises at least one of silicon oxide (SiO _2), lithium oxide (Li ₂ O), lead oxide (PbO) and tellurium oxide (TeO _2).
The method according to claim 1,
Wherein the glass frit comprises 6 to 19 mol% lead oxide, 1 to 10 mol% bismuth oxide, 11 to 24 mol% tellurium oxide, 31 to 44 mol% silicon oxide, 1 to 9 mol% zinc oxide, Mol% of tungsten oxide, 1 to 9 mol% of tungsten oxide, and 0.5 to 5 mol% of gallium oxide.
3. The method of claim 2,
Wherein the glass frit has a molar ratio of gallium oxide (Ga ₂ O ₃ ) and lead oxide (PbO) of 0.2: 1 to 1: 1.
3. The method of claim 2,
Wherein the glass frit has a molar ratio of gallium oxide (Ga ₂ O ₃ ) and tellurium oxide (TeO ₂ ) of from 0.15: 1 to 1: 1.
3. The method of claim 2,
The glass frit is silicon oxide (SiO ₂₎ and lithium oxide (Li ₂ O) in the glass frit content of the sum of 50 mol% to 80 mol% of.
3. The method of claim 2,
The glass frit is lead oxide (PbO) and tellurium oxide (TeO ₂₎ a glass frit content of the sum of 20 mol% to 35 mol% of.
3. The method of claim 2,
The glass frit is glass frit further comprises at least one of bismuth oxide (Bi ₂ O _3), zinc oxide (ZnO) and tungsten oxide (WO _3).
3. The method of claim 2,
The glass frit may be made of at least one selected from the group consisting of Bi, Zn, Na, Tl, P, Ge, Ce, (Mg), molybdenum (Mo), cesium (Cs), strontium (Sr), titanium (Ti), tin (Sn), indium (In), vanadium (V), barium (Ba) Further comprising at least one metal oxide selected from the group consisting of Cu, K, As, Cob, Zr, Mn and Al.
9. A PERC solar cell electrode-forming paste comprising glass frit, conductive powder, and organic vehicle according to any one of claims 1 to 9.
11. The method of claim 10,
The paste is a paste for forming a PERC solar cell electrode having a firing temperature of 700 ° C to 800 ° C.
11. The method of claim 10,
750 to 95% by weight of the conductive powder;
0.1 to 10% by weight of the glass frit; And
And 3 to 20% by weight of the organic vehicle.
11. The method of claim 10,
Wherein the paste further comprises at least one of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, a defoamer, a pigment, an ultraviolet stabilizer, an antioxidant and a coupling agent.
A PERC solar cell electrode made of the paste for forming the PERC solar cell electrode of claim 10.

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