KR101960465B1 - Conductive paste and solar cell - Google Patents

Abstract

A conductive glass powder, a metal glass including a first element having a heat of mixing with the conductive powder of less than 0, and a conductive paste containing an organic vehicle, and a solar cell using the conductive paste.

Description

CONDUCTIVE PASTE AND SOLAR CELL [0002]

Conductive pastes and solar cells.

The solar cell is a photoelectric conversion device that converts solar energy into electric energy, and is attracting attention as a next-generation energy resource with no pollution.

The solar cell includes a p-type semiconductor and an n-type semiconductor. When the solar energy is absorbed in the photoactive layer, an electron-hole pair (EHP) is generated inside the semiconductor, Type semiconductor and a p-type semiconductor, respectively, and they are collected in the electrode, so that they can be used as electric energy from the outside.

Solar cells are important to increase efficiency so that they can output as much electrical energy as possible from solar energy. In order to increase the efficiency of such a solar cell, it is also important to generate as many electron-hole pairs as possible in the semiconductor, but it is also important to draw out generated charges without loss.

On the other hand, the electrode of the solar cell can be formed by a screen printing method using a conductive paste.

One embodiment provides a conductive paste that can reduce the loss of charge and improve the efficiency of the solar cell.

Another embodiment provides a solar cell using the conductive paste.

According to one embodiment, there is provided a conductive paste comprising a conductive powder, a metal glass including a first element having a heat of mixing with the conductive powder of less than 0, and an organic vehicle.

The eutectic temperature of the conductive powder and the first element may be lower than the firing temperature of the conductive paste.

The firing temperature of the conductive paste may be about 1000 캜 or less.

The baking temperature of the conductive paste may be about 200 캜 to about 1000 캜.

The first element may be selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), promethidium (Pm), samarium (Sm), rutethium (Lu), yttrium (Y), neodymium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), thorium (Th), calcium (Ca), scandium (Sc) (Eu), zirconium (Zr), thallium (Tl), lithium (Li), and the like. (Au), plutonium (Pu), gallium (Ga), germanium (Ge), aluminum (Al), hafnium (Hf), magnesium (Mg), phosphorus (Cu), zinc (Zn), antimony (Sb), silicon (Si), tin (Sn), titanium (Ti), cadmium (Cd), indium (In), platinum (Pt) As shown in FIG.

The metal glass may further include a second element and a third element, and the metal glass may be an alloy having a composition represented by the following formula (1).

[Chemical Formula 1]

A _x -B _y -C _z

Wherein x, y, and z are the composition ratios of the first element, the second element, and the third element, and x + y + z = 1.

The first element, the second element, and the third element may be included in a ratio that satisfies the following relational expression (1).

[Relation 1]

xy? H ₁ + yz? H ₂ + zx? H ₃ <0

In the above relational expression 1,? H ₁ Is the mixed heat of the first element and the second element, ΔH ₂ The The mixed heat of the second element and the third element and the mixed heat of? H ₃ silver Is the mixed column of the third element and the first element.

The conductive powder may have a resistivity of about 100 mu OMEGA cm or less.

The conductive powder may include silver (Ag), aluminum (Al), copper (Cu), nickel (Ni), or a combination thereof.

The conductive powder, the metal glass, and the organic vehicle may be contained in an amount of about 30% by weight to about 99% by weight, about 0.1% by weight to about 20% by weight, respectively, based on the total amount of the conductive paste.

According to another embodiment, there is provided an electronic device including an electrode formed using the conductive paste.

According to another embodiment, there is provided a solar cell including a semiconductor layer, and an electrode electrically connected to the semiconductor layer and formed using the conductive paste.

The electrode may include a buffer layer located in a region adjacent to the semiconductor layer, and an electrode portion located in an area other than the buffer layer and containing a conductive material.

At least one of the buffer layer, the interface between the semiconductor layer and the buffer layer, and the semiconductor layer may include a crystallized conductive material.

The conductivity of the electrode can be improved and the contact resistance can be lowered by using the conductive paste according to this embodiment. Accordingly, the electrical characteristics of the electronic device using the electrode can be improved, and in the case of the solar cell, the charge can be efficiently collected and moved to the electrode side, thereby improving the efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a mixing column according to a content ratio of each element in a ternary alloy including Al-Cu-Zr,
FIGS. 2A to 2D are cross-sectional views schematically showing a state in which a conductive powder in a conductive paste according to an embodiment forms a solid solution and a solid solution in a metal glass,
3 is a cross-sectional view illustrating a solar cell according to one embodiment,
4 is a cross-sectional view illustrating a solar cell according to another embodiment.

Hereinafter, exemplary embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Hereinafter, the term &quot; element &quot; refers to a metal and a semimetal.

First, a conductive paste according to one embodiment will be described.

The conductive paste according to an embodiment includes a conductive powder, a metal glass including a first element having a heat of mixing with the conductive powder of less than 0, and an organic vehicle.

The conductive powder may be selected from a metal having a resistivity of about 100 mu OMEGA cm or less.

The conductive powder may be a silver-containing metal such as silver or a silver alloy, an aluminum-containing metal such as aluminum or an aluminum alloy, a copper-containing metal such as copper or a copper alloy, ) Or a nickel (Ni) containing metal such as a nickel alloy, or a combination thereof. However, it is not limited to this, and it may be a different kind of metal and may include other additives besides the metal.

The conductive powder may have a size of about 1 nm to about 50 탆.

The above-mentioned metal glass is an amorphous alloy having two or more kinds of elements having disordered atomic structure, and is also called an amorphous metal. Unlike ordinary glass such as silicate, metal glass has low resistivity and exhibits conductivity.

And the metal glass includes a first element whose mixing column with the conductive powder is less than zero. Here, the fact that the mixed heat is smaller than 0 means that spontaneous mixing thermodynamically occurs when the two materials are mixed in the molten state, and that the mixing heat of the conductive powder and the first element is smaller than 0 means that the conductive powder And the first element can spontaneously form a solid solution.

If the eutectic temperature of the conductive powder and the first element is lower than the firing temperature of the conductive paste, the conductive powder and the first element may be in a molten state during firing of the conductive paste, The conductive powder can be dissolved and diffused in the first element.

The firing temperature of the conductive paste may be about 1000 캜 or less, and may be about 200 캜 to about 1000 캜, so that an element capable of eutectic bonding with the conductive powder in the temperature range of the metal glass may be selected.

For example, when the conductive powder is a metal containing silver (Ag), the first element that can form a conductive powder and a solid solution at about 1000 ° C or lower is lanthanum (La), cerium (Ce), praseodymium (Pr) (Sm), rutethium (Lu), yttrium (Y), neodymium (Nd), gadolinium (Gd), terbium (Tb), dysprosium (Dy), horumium Bismuth Bi, germanium Ge, lead Pb, ytterbium (Yb), tungsten (Tm), thorium (Th), calcium (Ca), scandium (Sc), barium Ba, beryllium (Be) (Sr), Eu (Eu), Zr, Th, Li, Hf, Mg, Ph, As, (Au), plutonium (Pu), gallium (Ga), germanium (Ge), aluminum (Al), copper (Cu), zinc (Zn), antimony (Sb) , At least one selected from titanium (Ti), cadmium (Cd), indium (In), platinum (Pt) and mercury (Hg).

Here, the case where the conductive powder is silver (Ag) is exemplified, but the present invention is not limited thereto, and the conductive powder may be selected from various elements when it contains another metal.

The metal glass may be a ternary alloy containing a second element and a third element in addition to the first element.

When the metal glass is a ternary alloy, it may be represented by a composition represented by the following formula (1).

[Chemical Formula 1]

A _x -B _y -C _z

Wherein x, y, and z are the composition ratios of the first element, the second element, and the third element, and x + y + z = 1.

In the composition of the metallic glass, the composition ratio of the first element for increasing the solubility of the conductive powder may be included in a ratio satisfying the following relational expression (1).

[Relation 1]

xy? H ₁ + yz? H ₂ + zx? H ₃ <0

In the above relational expression 1,? H ₁ Is the mixed heat of the first element and the second element, ΔH ₂ The The mixed heat of the second element and the third element and the mixed heat of? H ₃ silver Is the mixed column of the third element and the first element.

When the total mixing heat of the metal glass is less than 0, the composition of the metal glass is thermodynamically stabilized, and the content ratio (x) of the first element which increases the solubility of the first element within the above range is determined .

The metal glass may be an alloy of two or more elements. For example, the first element may be aluminum (Al), and the second element and the third element may be copper (Cu) and zirconium (Zr), respectively.

In this case, when the Al, Cu, and Zr are ternary alloys including x%, y%, and z%, the mixed column value of Al-Cu is ΔH ₁ , the mixed column value of Cu-Zr is ΔH ₂ , When the mixed column value of Al is ΔH ₃ , The content of Al, which is the first element, can be determined within a range where xyΔH ₁ + yzΔH ₂ + zxΔH _{3, which} is the total mixed column value of the metal glass, has a value smaller than zero.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a mixing column according to a content ratio of each element in a ternary alloy including Al-Cu-Zr;

Referring to Figure 1, region A is the total heat of the mixed ternary alloy -10≤xyΔH yzΔH ₁ + ₂ + ₃ and zxΔH ≤-6 region satisfying the sphere B is the total heat of the mixed ternary alloys 2-6 the region that satisfies the _{≤xyΔH 1 + yzΔH 2 + zxΔH 3} ≤-3, C is a region in which the total mixture the column in the ternary alloy satisfies _{-3≤xyΔH 1 + yzΔH 2 + zxΔH 3} ≤0.

Referring to FIG. 1, x, y, and z values can be determined in a range having an appropriate total mixing row.

The metal glass may be, for example, Cu _{58 .1} Zr _{35 .9} Al ₆ and Cu ₄₆ Zr ₄₆ Al ₈ .

The organic vehicle includes the above-described conductive powder and an organic compound which can be mixed with the metallic glass to give an appropriate viscosity and a solvent for dissolving the organic compound.

The organic compound includes, for example, a (meth) acrylate-based resin; Cellulosic resins such as ethylcellulose; Phenolic resin; Alcohol resin; Teflon; And combinations thereof, and may further comprise additives such as surfactants, thickeners, and stabilizers.

The solvent is selected from the group consisting of terpineol, butyl carbitol, butyl carbitol acetate, pentanediol, diphentin, limonin, ethylene glycol alkyl ether, diethylene glycol alkyl ether, ethylene glycol alkyl ether acetate, diethylene glycol alkyl ether acetate, di Ethylene glycol dialkyl ether acetate, triethylene glycol alkyl ether acetate, triethylene glycol alkyl ether, propylene glycol alkyl ether, propylene glycol phenyl ether, dipropylene glycol alkyl ether, tripropylene glycol alkyl ether, propylene glycol alkyl ether acetate, dipropylene Glycol alkyl ether acetate, tripropylene glycol alkyl ether acetate, dimethyl phthalic acid, diethyl phthalic acid, dibutyl phthalic acid and demineralized water.

The conductive powder, the metal glass, and the organic vehicle may be contained in an amount of about 30% by weight to about 99% by weight, about 0.1% by weight to about 20% by weight, respectively, based on the total amount of the conductive paste.

The above-described conductive paste may be formed by a method such as screen printing and used as an electrode of an electronic device.

At this time, in the case of forming the electrode by applying the conductive paste on the semiconductor substrate, for example, as described above, the conductive powder may be diffused into the molten metal glass to form a solid solution with the metal glass including the first element.

This will be described with reference to FIGS. 2A to 2D.

FIGS. 2A to 2D are cross-sectional views schematically showing the case where the conductive paste according to an embodiment is applied to the semiconductor substrate 110, and the conductive powder forms a solid solution with the metal glass and diffuses into the metal glass.

Referring to FIG. 2A, a conductive paste 120a including a conductive powder 122a and a metal glass 115a is applied on a semiconductor substrate 110. FIG. The conductive powder 122a and the metal glass 115a may exist in the form of particles, respectively.

Referring to FIG. 2B, when the temperature of the metal glass 115a is increased to be higher than the glass transition temperature Tg of the metal glass 115a, the metal glass 115a softens to exhibit a liquid- 110 and a buffer layer 115 is formed thereon. The buffer layer 115 may be in close contact with the semiconductor substrate 110 and may contact the semiconductor substrate 110 over a large area. At this time, since the glass transition temperature Tg of the metallic glass 115a is lower than the sintering temperature of the conductive powder 122a, the conductive powder 122a may still exist in the form of particles. Thus, the electrode manufactured using the conductive paste may include a buffer layer 115 formed in a region adjacent to the semiconductor substrate 110, and an electrode portion formed in an area where the buffer layer 115 is not formed .

Referring to FIG. 2C, when the conductive powder 122a and the metal glass are heated to a temperature above the eutectic temperature, the conductive powder 122a and the metal glass are eutectic, and a part of the conductive powder 122a forms a solid solution with the metal glass, Lt; / RTI &gt;

A portion of the conductive powder 122a diffused into the buffer layer 115 may be diffused to the interface between the semiconductor substrate 110 and / or the semiconductor substrate 110 and the buffer layer 115. Referring to FIG. When the semiconductor substrate 110 is cooled, the conductive powder 122a is recrystallized to form the electrode part 120 composed of the crystallized conductive powder 122b, and the conductive powder 122c, which penetrates into the semiconductor substrate 110, It can also be recrystallized.

A buffer layer 115 made of a metal glass is formed between the electrode part 120 and the semiconductor substrate 110 and a conductive layer 122c is formed between the electrode part 120 and the semiconductor substrate 110, May penetrate into the semiconductor substrate 110 and be recrystallized.

The recrystallized conductive powder 122c present on the semiconductor substrate 110 can effectively transfer the charge generated in the semiconductor substrate 110 by the sunlight to the electrode unit 120 through the buffer layer 115 The contact resistance between the semiconductor substrate 110 and the electrode unit 120 can be reduced to reduce the charge loss of the solar cell. Thus, the efficiency of the solar cell can be increased.

A solar cell according to one embodiment will now be described with reference to FIG.

3 is a cross-sectional view illustrating a solar cell according to one embodiment.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Hereinafter, the positional relationship between the semiconductor substrate 110 and the semiconductor substrate 110 will be described for convenience of explanation, but the present invention is not limited thereto. Also, the surface of the semiconductor substrate 110 which receives solar energy is referred to as a front side, and the opposite surface of the semiconductor substrate 110 is referred to as a rear side.

Referring to FIG. 3, a solar cell according to an embodiment includes a semiconductor substrate 110 including a lower semiconductor layer 110a and an upper semiconductor layer 110b.

The semiconductor substrate 110 may be made of crystalline silicon or a compound semiconductor, and in the case of crystalline silicon, for example, a silicon wafer may be used. One of the lower semiconductor layer 110a and the upper semiconductor layer 110b may be a semiconductor layer doped with a p-type impurity and the other may be a semiconductor layer doped with an n-type impurity. For example, the lower semiconductor layer 110a may be a semiconductor layer doped with a p-type impurity, and the upper semiconductor layer 110b may be a semiconductor layer doped with an n-type impurity. The p-type impurity may be a Group III compound such as boron (B), and the n-type impurity may be a Group V compound such as phosphorus (P).

The surface of the upper semiconductor layer 110b may be surface textured. The surface-structured upper semiconductor layer 110b may be a porous structure such as a pyramid-like irregularity or a honeycomb-like structure. The surface-structured upper semiconductor layer 110b may increase the surface area receiving light to increase the light absorption rate and reduce the reflectivity, thereby improving the efficiency of the solar cell.

A plurality of front electrodes are formed on the upper semiconductor layer 110b. The front electrodes extend along one direction of the substrate and can be designed with a grid pattern in consideration of light absorption loss and sheet resistance.

The front electrode may include a buffer layer 115 located in a region adjacent to the upper semiconductor layer 110b and a front electrode unit 120 disposed in a region other than the buffer layer 115 and containing a conductive material. Although the buffer layer 115 is illustrated in FIG. 3, the buffer layer 115 is not limited thereto, and the buffer layer 115 may be omitted. In addition, the buffer layer 115 may be located only in a portion of the region adjacent to the upper semiconductor layer 110b.

The front electrode may be formed by a screen printing method using a conductive paste. The conductive paste is as described above.

The front electrode unit 120 may be made of a conductive material such as silver (Ag), aluminum (Al), copper (Cu), nickel (Ni), or a combination thereof.

A buffer layer 115 is formed between the upper semiconductor layer 110b and the front electrode part 120. The buffer layer 115 is as described above and has conductivity including metal glass. Since the buffer layer 115 has a portion in contact with the front electrode portion 120 and a portion in contact with the upper semiconductor layer 110b so that charges can move between the upper semiconductor layer 110b and the front electrode portion 120 The area of the path can be widened to reduce the loss of charge.

The metal glass included in the buffer layer 115 is a component included in the conductive paste of the front electrode part 120 and is melted prior to the conductive material of the front electrode part 120 during the process, Can be located.

The buffer layer 115 includes crystallized conductive material 122c at an interface between the upper semiconductor layer 110b and / or the upper semiconductor layer 110b and the buffer layer 115 located under the buffer layer 115. The crystallized conductive material 122c is melted in the baking step when the front electrode is formed using the conductive paste and is crystallized after passing through the buffer layer 115 and diffused into the upper semiconductor layer 110b, The contact resistance between the upper semiconductor layer 110b and the front electrode part 120 can be lowered and the electrical characteristics of the solar cell can be improved.

A front bus bar electrode (not shown) is formed on the front electrode part 120. The bus bar electrode is for connecting neighboring solar cells when assembling a plurality of solar cells.

A dielectric layer 130 is formed under the semiconductor substrate 110. The dielectric layer 130 prevents the recombination of charges and prevents leakage of current, thereby increasing the efficiency of the solar cell. The dielectric layer 130 has a plurality of penetration portions 135. The semiconductor substrate 110 and the rear electrode described later may be in contact with each other through the penetration portions 135. [

The dielectric layer 130 may be made of, for example, silicon oxide (SiO ₂ ), silicon nitride (SiN _x ), aluminum oxide (Al ₂ O ₃ ), or combinations thereof and may have a thickness of about 100 Å to about 2000 Å.

A rear electrode is formed under the dielectric layer 130. The backside electrode may be made of a conductive material, and may be made of an opaque metal such as aluminum (Al). The back electrode may be formed by a screen printing method using a conductive paste in the same manner as the front electrode.

The rear electrode may include a buffer layer 115 located in a region adjacent to the lower semiconductor layer 110a as in the front electrode, and a rear electrode unit 140 located in a region other than the buffer layer and containing a conductive material . Although the buffer layer 115 is illustrated in FIG. 3, the buffer layer 115 is not limited thereto, and the buffer layer 115 may be omitted. In addition, the buffer layer 115 may be located only in a portion of the region adjacent to the lower semiconductor layer 110a.

The interface between the buffer layer 115 and the lower semiconductor layer 110a and / or the lower semiconductor layer 110a and the buffer layer 115 located above the buffer layer 115 includes a crystallized conductive material 122c. The crystallized conductive material 122c is melted in the baking step when the back electrode is formed using the conductive paste and is crystallized after passing through the buffer layer 115 and diffused into the lower semiconductor layer 110a and is crystallized with the buffer layer 115 The contact resistance between the lower semiconductor layer 110a and the rear electrode part 140 can be lowered and the electrical characteristics of the solar cell can be improved.

Hereinafter, a manufacturing method of the solar cell will be described with reference to FIG.

First, a semiconductor substrate 110 such as a silicon wafer is prepared. At this time, the semiconductor substrate 110 may be doped with a p-type impurity, for example.

Then, the semiconductor substrate 110 is surface-structured. The surface texture can be carried out by a wet process using strong base solutions such as, for example, nitric acid and hydrofluoric acid or sodium hydroxide, or by a dry process using a plasma.

Next, the semiconductor substrate 110 is doped with an n-type impurity, for example. Here, the n-type impurity can be doped by diffusing POCl ₃ or H ₃ PO ₄ at a high temperature. Accordingly, the semiconductor substrate 110 includes a lower semiconductor layer 110a doped with another impurity and an upper semiconductor layer 110b.

And the front electrode conductive paste is applied on the upper semiconductor layer 110b. The conductive paste for the front electrode can be formed by a screen printing method. Screen printing involves applying the conductive paste described above, including conductive powder, metallic glass, and an organic vehicle, to the locations where the electrodes will be formed and drying.

The conductive paste may include a metallic glass as described above, and the metallic glass may be formed by, for example, melt spinning, infiltration casting, gas atomization, ion irradiation, or mechanical alloying mechanical alloying, or the like.

Then, the conductive paste for the front electrode is dried.

Next, aluminum oxide (Al ₂ O ₃ ) or silicon oxide (SiO ₂ ) is laminated on the rear surface of the semiconductor substrate 110 by a plasma chemical vapor deposition method to form a dielectric film 130.

Then, a plurality of penetration portions 135 are formed by irradiating a part of the dielectric film 130 with a laser.

Next, a conductive paste for a rear electrode is applied to one surface of the dielectric layer 130 by a screen printing method and dried.

Subsequently, the conductive paste for the rear electrode is dried.

Then, the conductive paste for the front electrode and the conductive paste for the rear electrode are co-fired. However, the present invention is not limited thereto, and the conductive paste for the front electrode and the conductive paste for the rear electrode can be fired, respectively.

The firing may be performed at a temperature higher than the melting temperature of the conductive metal in the firing furnace, and may be performed at, for example, about 200 ° C to about 1000 ° C.

Hereinafter, a solar cell according to another embodiment will be described with reference to FIG.

4 is a cross-sectional view illustrating a solar cell according to another embodiment.

The solar cell according to this embodiment includes a semiconductor substrate 110 doped with a p-type or n-type impurity. The semiconductor substrate 110 includes a plurality of first doped regions 111a and a plurality of second doped regions 111b which are formed on the back side and doped with different impurities. The first doped region 111a may be doped with, for example, an n-type impurity, and the second doped region 111b may be doped with, for example, a p-type impurity. The first doped region 111a and the second doped region 111b may be alternately arranged on the rear surface of the semiconductor substrate 110. [

The front surface of the semiconductor substrate 110 may be surface-structured, and the efficiency of the solar cell may be improved by increasing the light absorption rate and reducing the reflectivity by surface texture.

An insulating film 112 is formed on the semiconductor substrate 110. The insulating film 112 may be made of a material that absorbs less light and is insulating and may be made of a material such as silicon nitride (SiN _x ), silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ) magnesium oxide (MgO), it may be a cerium oxide (CeO _2), and combinations thereof, may be formed of a single layer or multiple layers. The insulating film 112 may have a thickness of, for example, about 200 Å to about 1500 Å.

The insulating layer 112 serves as an anti-reflective coating that reduces the reflectivity of light on the surface of the solar cell and increases the selectivity of a specific wavelength region, and also improves the contact property with silicon on the surface of the semiconductor substrate 110 Thereby increasing the efficiency of the solar cell.

On the rear surface of the semiconductor substrate 110, a dielectric film 150 having a plurality of penetration portions is formed.

A first electrode connected to the first doped region 111a and a second electrode connected to the second doped region 111b are formed on the rear surface of the semiconductor substrate 110, respectively. The first electrode may be connected to the first doped region 111a through the penetrating portion and the second electrode may be connected to the second doped region 111b through the penetrating portion. The first electrode and the second electrode may be arranged alternately.

The first electrode includes a buffer layer 115 located in a region adjacent to the first doped region 111a and a first electrode portion 121 located in a region other than the buffer layer 115, A buffer layer 115 located in a region adjacent to the doped region 111b and a second electrode portion 141 located in an area other than the buffer layer 115. [ Although the buffer layer 115 is illustrated in FIG. 4, the buffer layer 115 is not limited thereto, and the buffer layer 115 may be omitted. Also, the buffer layer 115 may be located only in a portion of the region adjacent to the first doped region 111a, a portion of the region adjacent to the second doped region 111b, or a combination thereof.

The first electrode and the second electrode may be formed using a conductive paste including conductive powder, metal glass, and an organic vehicle, as described above, and the detailed description thereof is as described above.

A buffer layer 115 is formed between the first doped region 111a and the first electrode portion 121 and between the second doped region 111b and the second electrode portion 141. Since the buffer layer 115 includes a metal glass as described above, the buffer layer 115 is conductive and has a portion contacting the first electrode portion 121 or the second electrode portion 141 and a portion contacting the first doped region 111a or the second doped region 111. [ The charge can move between the first doped region 111a and the first electrode portion 121 or between the second doped region 111b and the second electrode portion 141 The area of the passage can be widened to reduce the loss of charge.

The interface between the buffer layer 115, the first doped region 111a, the second doped region 111b, the first doped region 111a and the buffer layer 115, the second doped region 111b of the semiconductor substrate 110, And at least one of the interfaces of the buffer layer 115 and the buffer layer 115 includes a crystallized conductive material 122c. The crystallized conductive material 122c is melted in the firing step at the time of forming the first electrode and / or the second electrode using the conductive paste and passes through the buffer layer 115 to form the first doped region 111a of the semiconductor substrate 110, The first doped region 111a and the second doped region 111b and the first doped region 111b and the second doped region 111b are crystallized after being diffused into the first doped region 111b and / The contact resistance between the two electrode portions 141 can be lowered and the electrical characteristics of the solar cell can be improved.

In the solar cell according to this embodiment, since the first electrode and the second electrode are both located on the rear surface of the solar cell, the area occupied by the metal can be reduced to reduce the light absorption loss, Can be increased.

Hereinafter, a method of manufacturing a solar cell according to this embodiment will be described with reference to FIG.

First, a semiconductor substrate 110 doped with an n-type impurity, for example, is prepared. Next, after the semiconductor substrate 110 is surface-structured, an insulating film 112 and a dielectric film 150 are formed on the front and rear surfaces of the semiconductor substrate 110. The insulating film 112 and the dielectric film 150 can be formed, for example, by chemical vapor deposition.

Next, a first doped region 111a and a second doped region 111b are formed by doping, for example, a p-type impurity and an n-type impurity in high concentration on the back surface side of the semiconductor substrate 110 in this order.

Next, a first electrode conductive paste is applied to a region corresponding to the first doped region 111a on one surface of the dielectric layer 150, and a second electrode conductive paste is applied to a region corresponding to the second doped region 111b . The conductive paste for the first electrode and the conductive paste for the second electrode may be formed by a screen printing method, respectively, and the conductive paste containing the conductive powder, the metal glass and the organic vehicle may be used.

The conductive paste for the first electrode and the conductive paste for the second electrode may be fired together or individually, and the firing may be performed at a temperature higher than the melting temperature of the conductive metal in the firing furnace.

In the foregoing, only the example of applying the conductive paste as an electrode of a solar cell has been specifically described. However, the present invention is not limited to this, and can be applied to all electronic devices including electrodes.

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

silver( Ag ) &Lt; / RTI &

Example  One

Metal glass Cu ₄₆ Zr ₄₆ Al ₈ is prepared in the form of a ribbon having a thickness of 90 μm and a width of 0.5 cm. The metal glass ribbon is cut into a length of 1 cm, and then silver (Ag) paste containing 85% by weight of silver (Ag) is applied thereon. Next, the metal glass ribbon is heat-treated at 650 ° C for 30 minutes in the air to form a conductive thin film. The rate of temperature rise is 50 ° C / min.

Example  2

And to form a conductive thin film on the metallic glass ribbon in the same manner as in Example 1 except for using a Cu ₄₆ Zr ₄₆ Al ₈ instead of Cu ₅₈ Zr _{35 .1 .9} Al ₆ a metallic glass.

Comparative Example  One

A conductive thin film was formed on a metallic glass ribbon in the same manner as in Example 1, except that Cu ₅₀ Zr ₅₀ was used instead of Cu ₄₆ Zr ₄₆ Al ₈ as the metallic glass.

Rating - 1

The metallic glass ribbon and the conductive thin film formed according to Examples 1 and 2 and Comparative Example 1 were cut, and their cross sections were analyzed.

Table 1 shows the solubility of silver (Ag) present in the metallic glass ribbon at a position about 3 탆 away from the interface between the metallic glass ribbon and the conductive thin film in Examples 1 and 2 and Comparative Example 1. The degree of solubility of silver (Ag) was measured by the energy dispersive X-ray spectroscopy (EDS) at the interface between the metallic glass ribbon and the conductive thin film, and the concentration (at%) of silver (Ag) .

The solubility (at%) of silver (Ag) Example 1 8 Example 2 5 Comparative Example 1 One

Referring to Table 1, it can be seen that the metal glass ribbon formed according to Examples 1 and 2 has a larger amount of silver (Ag) than the metal glass ribbon formed according to Comparative Example 1. Further, it can be seen that Example 1 using a metal glass having a high aluminum (Al) content has higher solubility of silver (Ag) than Example 2.

Manufacture of conductive paste and electrode

Example  3

Silver (Ag) powder and metallic glass Cu ₄₆ Zr ₄₆ Al ₈ are added to an organic vehicle containing ethyl cellulose binder and butyl carbitol solvent. At this time, the silver (Ag) powder, the metallic glass Cu ₄₆ Zr ₄₆ Al ₈ and the organic vehicle are mixed at about 84 wt%, about 4 wt% and about 12 wt%, respectively, relative to the total content of the conductive paste.

And then kneaded using a three-roll mill to prepare a conductive paste.

The above conductive paste is applied onto a silicon wafer by a screen printing method. Subsequently, the mixture is rapidly heated to about 500 ° C using a belt furnace and slowly heated to about 900 ° C. Thereafter, the electrode is formed by cooling.

Example  4

After the conductive paste is manufactured in the same manner as in Example 3 except for using a Cu ₄₆ Zr ₄₆ Al ₈ instead of Cu ₅₈ Zr _{35 .1 .9} Al ₆ a metallic glass to form an electrode.

Comparative Example  2

A conductive paste was prepared in the same manner as in Example 3 except that Cu ₅₀ Zr ₅₀ was used instead of Cu ₄₆ Zr ₄₆ Al ₈ as a metal glass, and then an electrode was formed.

Rating - 2

The contact resistance values of the electrodes formed according to Examples 3 and 4 and Comparative Example 2 are measured. The contact resistance value is measured by the Transfer length method (TLM)

Table 2 shows the contact resistance values of the electrodes formed according to Examples 3 and 4 and Comparative Example 2.

Contact resistance (mΩ ㎠) Example 3 35.60 Example 4 40.07 Comparative Example 2 60.57

Referring to Table 2, it can be seen that the electrodes according to Examples 3 and 4 have lower contact resistance values as compared with the electrodes according to Comparative Example 2. From this, it can be seen that the contact resistance can be lowered by using a metal glass including silver (Ag) and aluminum (Al) capable of solubility. Further, by using a metal glass having a higher content of aluminum (Al), it is possible to further increase the solubility with silver (Ag) and further reduce the contact resistance value.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

110: semiconductor substrate 115a: metal glass
115: buffer layer 120: front electrode part
122a: conductive powder 122b, 122c: crystallized conductive powder
121: first electrode part 130: dielectric film
135: penetrating part 140: rear electrode part
141: second electrode portion

Claims (14)

Conductive powder,
A metal glass comprising a first element having a heat of mixing with the conductive powder of less than 0, and
Organic vehicle
/ RTI &gt;
Wherein the organic vehicle comprises a solvent,
Wherein the solvent is selected from the group consisting of terpineol, butyl carbitol, butyl carbitol acetate, pentanediol, diphentin, limonin, ethylene glycol alkyl ethers, diethylene glycol alkyl ethers, ethylene glycol alkyl ether acetates, diethylene glycol alkyl ether acetates, Diethylene glycol dialkyl ether acetate, triethylene glycol alkyl ether acetate, triethylene glycol alkyl ether, propylene glycol alkyl ether, propylene glycol phenyl ether, dipropylene glycol alkyl ether, tripropylene glycol alkyl ether, propylene glycol alkyl ether acetate, di At least one selected from propylene glycol alkyl ether acetate, tripropylene glycol alkyl ether acetate, dimethyl phthalic acid, diethyl phthalic acid, dibutyl phthalic acid and demineralized water.
The method of claim 1,
Wherein the eutectic temperature of the conductive powder and the first element is lower than the firing temperature of the conductive paste.
3. The method of claim 2,
Wherein the baking temperature of the conductive paste is 200 占 폚 to 1000 占 폚.
delete The method of claim 1,
The first element may be selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), promethidium (Pm), samarium (Sm), rutethium (Lu), yttrium (Y), neodymium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), thorium (Th), calcium (Ca), scandium (Sc) (Eu), zirconium (Zr), thallium (Tl), lithium (Li), and the like. (Au), plutonium (Pu), gallium (Ga), germanium (Ge), aluminum (Al), hafnium (Hf), magnesium (Mg), phosphorus (Cu), zinc (Zn), antimony (Sb), silicon (Si), tin (Sn), titanium (Ti), cadmium (Cd), indium (In), platinum (Pt) &Lt; / RTI &gt;
The method of claim 1,
Wherein the metal glass further comprises a second element and a third element,
Wherein the metal glass is a conductive paste which is an alloy having a composition represented by the following Chemical Formula 1:
[Chemical Formula 1]
A _x -B _y -C _z
Wherein x, y, and z are the composition ratios of the first element, the second element, and the third element, and x + y + z = 1.
The method of claim 6,
Wherein the first element, the second element, and the third element are contained in a ratio satisfying the following relational expression 1:
[Relation 1]
xy? H ₁ + yz? H ₂ + zx? H ₃ <0
In the above relational expression 1,? H ₁ Is the mixed heat of the first element and the second element, ΔH ₂ The The mixed heat of the second element and the third element and the mixed heat of? H ₃ silver Is the mixed column of the third element and the first element.
The method of claim 1,
Wherein the conductive powder has a resistivity of 100 占 cm or less.
The method of claim 1,
Wherein the conductive powder includes silver (Ag), aluminum (Al), copper (Cu), nickel (Ni), or a combination thereof.
The method of claim 1,
Wherein the conductive powder, the metallic glass, and the organic vehicle are contained in an amount of 30 to 99% by weight, 0.1 to 20% by weight, respectively, based on the total amount of the conductive paste.
An electronic device comprising an electrode formed using the conductive paste according to any one of claims 1 to 3 and 5 to 10.
Semiconductor layer, and
An electrode electrically connected to the semiconductor layer and formed using the conductive paste according to any one of claims 1 to 3 and 5 to 10,
&Lt; / RTI &gt;
The method of claim 12,
Wherein the electrode comprises a buffer layer located in a region adjacent to the semiconductor layer, and an electrode portion located in an area other than the buffer layer and containing a conductive material.
The method of claim 13,
Wherein at least one of the buffer layer, the interface between the semiconductor layer and the buffer layer, and the semiconductor layer includes a crystallized conductive material.

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