KR20140003669A - Solar cell and manufacturing method thereof - Google Patents

Abstract

A solar cell according to the embodiment of the present invention has a substrate having a first conductivity type, an emitter layer located on a first side of the substrate having a second conductivity type, a first dielectric layer portion situated on the emitter layer, a second dielectric layer portion located at the rear of the first substrate, and a second electrode portion connected to the emitter layer and the first electrode portion. The emitter layer includes a first texturing surface having a plurality of first projection parts and a second texturing surface located on the surface of the first projection part and has a plurality of second projection parts that are smaller than the first projection parts. The second projection part is located on a peak of at least one of the many first projection parts.

Description

SOLAR CELL AND MANUFACTURING METHOD THEREOF {SOLAR CELL AND MANUFACTURING METHOD THEREOF}

The present invention relates to a solar cell and a method of manufacturing the same.

Recently, as energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing, and solar cells that produce electric energy from solar energy are attracting attention.

Typical solar cells have a semiconductor portion that forms a p-n junction by different conductivity types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types.

When light is incident on the solar cell, charges (electrons and holes) are generated in the semiconductor, and the generated charges move to the n-type and p-type semiconductors by pn junctions. Move toward the p-type semiconductor portion.

The moved electrons and holes are collected by different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the efficiency of a solar cell.

According to one aspect of the present invention, a solar cell includes a substrate having a first conductivity type; An emitter portion disposed on the first surface of the substrate and having a second conductivity type; A first dielectric layer portion located over the emitter portion; A second dielectric layer portion located on the back side of the substrate; A first electrode part connected to the emitter part; And a second electrode part connected to the substrate. And the emitter portion includes a first texturing surface comprising a plurality of first protrusions, and a second texturing surface located on the surface of the first protrusion and including a plurality of second protrusions of a smaller size than the first protrusion. The second protrusion is also located at a peak of at least one first protrusion of the plurality of first protrusions.

The second protrusion may also be located in a valley of at least one of the first protrusions of the plurality of first protrusions.

Each of the first protrusions is formed in a size of 5 μm to 15 μm, and each of the second protrusions is formed in a size of 200 nm to about 600 nm. Here, the size includes a maximum width and a maximum height of each of the first protrusion and the second protrusion.

The ratio (a / b) of the length (a) of the imaginary line connecting vertices and the length (b) of the straight line connecting the starting point and the end point of the imaginary line is 1.1 to 1.3 in the vertical section of the second protrusions. Distribute as much as possible. In this case, the ratio a / b is a value measured for three or more second protrusions.

The second dielectric layer portion includes a first dielectric layer overlying the backside of the substrate and a second dielectric layer overlying the first dielectric layer, wherein the first dielectric layer portion includes a second dielectric layer overlying the emitter portion and a third dielectric layer overlying the second dielectric layer. Include.

The first dielectric layer and the third dielectric layer each consist of hydrogenated silicon nitride having a thickness of 70 nm to 100 nm, and the second dielectric layer consists of aluminum oxide having a thickness of 5 nm to 15 nm.

The second dielectric layer portion further includes a hydrogenated silicon oxide film positioned between the first dielectric layer and the second dielectric layer, wherein the hydrogenated silicon oxide film has a thickness of 50 nm to 100 nm.

A silicon oxide film having a thickness of 2 nm to 3 nm may be further disposed between the second surface of the substrate and the first dielectric layer.

The first texturing surface and the second texturing surface are formed on both the first side and the second side of the substrate, and light may be incident through the first side and the second side of the substrate, respectively.

A hydrogenated silicon oxide layer having a thickness of 50 nm to 100 nm may be further disposed on the third dielectric layer.

A silicon oxide film having a thickness of 2 nm to 3 nm may be further disposed between the emitter portion and the second dielectric layer.

In a method of manufacturing a solar cell according to an embodiment of the present invention, performing anisotropic etching using an alkaline etching solution to form a first textured surface including a plurality of first protrusions on at least one side of a substrate. ; Forming at least one of a peak and a valley of the first protrusion as a curved surface by performing isotropic etching using an acid etchant to etch back the plurality of first protrusions; Performing a dry etching process to form a second texturing surface on the surface of the first protrusion, the second texturing surface comprising a plurality of second protrusions formed in a smaller size than the first protrusion; And implanting impurity ions into the first texturing surface and the second texturing surface by performing an ion implantation process, and performing an activation process to form an emitter portion. In this case, the second protrusion may be formed on a peak of at least one of the first protrusions.

The second protrusion may be formed in a valley of at least one first protrusion of the plurality of first protrusions.

When performing a dry etching process, reactive ion etching (RIE) may be used.

In the manufacturing method according to the embodiment of the present invention, the first texturing surface and the second texturing surface are formed on both the first and second surfaces of the substrate, the emitter portion is formed on the first surface of the substrate, On the two sides, the rear electric field is formed locally.

Herein, 'locally forming the rear electric field portion' means forming the rear electric field portion only at a position corresponding to the finger electrode constituting the second electrode portion.

Therefore, the rear electric field portion is formed in the same pattern as the plurality of finger electrodes of the second electrode portion.

The emitter part is formed by implanting and activating a first impurity ion, and the rear field part is formed by implanting and activating a second impurity ion having a conductivity opposite to that of the first impurity ion, and activating the first impurity ion and the second impurity ion. The process is carried out for 20 to 60 minutes at a temperature of 1000 ° C to 2000 ° C at which the first impurity ions are activated.

The first and second surfaces of the substrate damaged by the dry etching process are removed using an activation process.

A manufacturing method according to an embodiment of the present invention includes forming a first dielectric layer on a second side of a substrate; Simultaneously forming a second dielectric layer over the emitter portion and over the first dielectric layer located on the second side of the substrate; Forming a third dielectric layer over the second dielectric layer located over the emitter portion; And forming a first electrode part connected to the emitter part and a second electrode part connected to the rear electric field part.

The first dielectric layer and the third dielectric layer are formed by depositing hydrogenated silicon nitride to a thickness of 70 nm to 100 nm, respectively, and the second dielectric layer is formed by depositing aluminum oxide to a thickness of 5 nm to 15 nm. Deposition is carried out using atomic layer deposition.

The manufacturing method according to the embodiment of the present invention may further include depositing hydrogenated silicon oxide to a thickness of 50 nm to 100 nm between the first dielectric layer and the second dielectric layer, and over the third dielectric layer.

The method may further include forming a silicon oxide film having a thickness of 2 nm to 3 nm by immersing the substrate in nitric acid having a Ph concentration of 2 to 4 for 5 minutes to 30 minutes before forming the first dielectric layer.

According to this aspect, the present invention is anisotropic etching using an alkaline etching solution to form a plurality of first protrusions, and then isotropically etching using an acid etchant to etch back the plurality of first protrusions to peak the first protrusions At least one of the and valleys is formed in a curved surface, and then a dry etching process is performed to form a plurality of second protrusions.

As described above, the present invention, which performs two wet etching processes to form the first protrusions, may form the first protrusions by one wet etching process using either one of an alkaline etchant or an acid etchant, followed by a dry etching process. As a result, the following effects can be obtained as compared with the conventional art of forming the second protrusions.

First, when the first protrusion is formed by anisotropic etching using an alkaline etchant, and the second protrusion is formed by a dry etching process, the first protrusion is formed by anisotropic etching using an acid etchant, followed by a dry etching process. Compared to the case of forming the second protrusion, the short-circuit current density (Jsc) is lower and the life time is shorter. However, the present invention is similar to the case of forming the first protrusion by anisotropic etching using an acid etchant. Short circuit current density and life time can be obtained.

In addition, when the first protrusion is formed by anisotropic etching using an acid etchant, and the second protrusion is formed by a dry etching process, the first protrusion is formed by anisotropic etching using an alkaline etchant, followed by a dry etching process. 2 Although the recombination property is lowered at the peak of the first protrusion compared to the case where the protrusion is formed, and thus the reverse current (Irev, reverse current) characteristic is low, the present invention provides a first protrusion by anisotropic etching using an alkaline etchant. After forming the present invention, a reverse current (Irev) characteristic similar to the case of forming the second protrusion by the dry etching process is shown.

In addition, since the peak of the first protrusion is very sharp in the prior art in which the first protrusion is formed only by one wet etching process, the second protrusion is not formed at the peak of the first protrusion, and thus the surface recombination rate (surface recombination velocity) characteristics are reduced, there is a problem that the reduction in the open voltage and the passivation characteristics, but the present invention forms a second projection after forming the peak of the first projection to the curved surface, so that the peak of the first projection The second protrusion of the desired shape can be formed uniformly.

Therefore, the surface recombination rate characteristic can be improved, the open voltage can be increased, and the passivation characteristic can be improved.

In addition, since the anti-reflection portion and the protection portion made of a multilayer film are located on the front and rear surfaces of the substrate, the amount of light reflection is reduced and the surface passivation effect occurs on the surface of the substrate, thereby further improving the efficiency of the solar cell.

In addition, since the silicon oxide film is thinly coated on at least one of the front and rear surfaces of the substrate, the problem caused by the natural oxide film is reduced, so that the efficiency of the solar cell is further improved.

In addition, since the size and uniformity of the second protrusions formed on the first texturing surface are optimized, the reflectivity of light is maintained in an optimized range, for example 7% to 10%. Therefore, the conversion efficiency can be effectively improved.

1 is a partial perspective view of a solar cell according to an embodiment of the present invention.
2 is a view for explaining an example in which a plurality of protrusions having a pyramid shape according to the present invention has a curved surface at the corner portion of the inclined surface.
3 is an enlarged view of a main part of FIG. 1.
4 is a conceptual diagram for showing a ratio of the surface area / real area of the second texturing surface.
5A to 5H are diagrams sequentially illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
FIG. 6 is a diagram specifically illustrating a method of forming the first texturing surface shown in FIG. 5A and the second texturing surface shown in FIG. 5B.
7 is a graph measuring the life time of the hydrogenated silicon nitride film according to Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention.
8 is a partial cross-sectional view of a solar cell according to another embodiment of the present invention.
9 and 10 are partial cross-sectional views of a solar cell according to still another embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement 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. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above 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.

In addition, when a part is formed "overall" on another part, it means that not only is formed on the entire surface of the other part but also is not formed on a part of the edge.

Next, a solar cell and a manufacturing method thereof according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

First, a solar cell according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 1.

Referring to FIG. 1, a solar cell according to an embodiment of the present invention may include a substrate 110, an emitter region 121 positioned on a front surface (first surface) of the substrate 110, The first dielectric layer portion 130 positioned on the emitter portion 121 and the second dielectric layer portion 190 positioned on the back surface (second surface) of the substrate 110 positioned opposite to the front surface of the substrate 110. And a plurality of front electrodes (a plurality of first finger electrodes) and a plurality of front bus bars 142 (a plurality of first bus bars) when located on the front surface of the substrate 110 and connected to the emitter unit 121. Located on the front electrode portion (first electrode portion) 140, the back of the substrate 110 and having a plurality of rear electrodes (plural second finger electrodes) and a plurality of rear bus bars (plural second bus bars) The back electrode part (second electrode part) 150 and the rear electric field part (back) located on the rear side of the substrate 110 and positioned under the plurality of back electrodes 151 and the bottom of the plurality of rear busbars 152. surface field) 172.

In this embodiment, light is incident on at least one of the front and rear surfaces of the substrate 110.

The substrate 110 is a semiconductor substrate made of a semiconductor such as silicon of a first conductivity type, for example, an n-type conductivity. At this time, the semiconductor is a crystalline semiconductor made of single crystal silicon. The n-type substrate 110 is doped with impurities of pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb).

A texturing treatment process is performed on the front surface of the substrate 110, and the front surface of the substrate 110 is formed of a first textured surface that is an uneven surface having a plurality of first protrusions 11 protruding upward from the periphery. . In this case, the emitter 121 and the first dielectric layer 130 disposed on the front surface of the substrate 110 also have an uneven surface.

At this time, the shape of the first protrusion 11 has a pyramid shape.

In the present embodiment, the size of the first protrusion 11, that is, the maximum width a and the maximum height b may be about 5 μm to 15 μm, respectively, and the aspect ratio of the first protrusion 11 is determined. (b / a) is about 1.0 to 1.5.

As the plurality of first protrusions 11 are positioned on the front surface of the substrate 110, the incident area of the substrate 110 increases and the light reflectivity decreases by a plurality of reflection operations by each of the protrusions 11. Since the amount of light incident on the 110 increases, the efficiency of the solar cell is improved.

Hereinafter, the plurality of first protrusions 11 formed on the incident surface of the substrate 110 will be described.

In FIG. 2, (a) shows a plurality of first protrusions 11 formed on the incident surface of the substrate 110, (b) shows a three-dimensional shape of the first protrusion 11, and (c ) Shows a cross section of the first protrusion 11, and (d) shows a plan view of the first protrusion 11 viewed from above.

As shown in FIG. 2A, a plurality of first protrusions 11 are formed on the front surface of the substrate 110 according to the present invention. The plurality of first protrusions 11 may be formed on the rear surface of the substrate 110 as shown in FIG. 1, but may not be formed on the rear surface of the substrate 110.

As shown in (b) and (c) of FIG. 2, the first protrusion 11 has a pyramid shape, and the peak TP1 of the protrusion 11 is formed as a curved surface. In this case, the edge portion EP1 connecting the inclined surface SP1 and the valley VP1 connecting the adjacent first protrusion 11 may also have a curved shape.

As such, the peak TP1, the valley VP1, and the corner portion EP1 of the inclined surface SP1 of the first protrusion 11 are formed to have a curved surface, thereby forming the first surface formed on the incident surface of the substrate 110. The dielectric layer 130 may be formed more uniformly at the peak TP1, the valley VP1, and the corner portion EP1 of the inclined surface SP1.

In this case, the diameters R1, R2, and R3 of the curved portion EP1, the peak TP1, and the valley VP1 of the inclined surface SP1 of the first protrusion 11 may be 5 nm or more and 15 nm or less, respectively.

Herein, the diameters R1, R2, and R3 of the curved surface may be 5 nm or more at the edge portion EP1, the peak TP1, and the valley VP1 of the first dielectric layer 130 in the inclined surface SP1. This is to form a uniform.

In addition, the diameter of the curved surface (R1, R2, R3) to 15nm or less is to minimize the reflection on the incident light. That is, when the diameters R1, R2, and R3 of the curved surface are 15 nm or more, the uniformity of the first dielectric layer 130 formed on the first protrusion 11 is further improved, but the reflectivity to light is increased. Therefore, it is preferable to make diameter (R1, R2, R3) of a curved surface into 15 nm or less.

Here, the diameters R1, R2, and R3 of the curved surfaces may be the same as or different from each other within the above range.

The maximum width a of the first protrusion 11 may be formed in a range of 5 μm or more and 15 μm or less. The size of the first protrusion 11 is larger as the maximum width a becomes larger and smaller as the maximum width a becomes smaller due to the characteristics of the crystalline silicon forming the substrate 110.

Therefore, the maximum width a of the first protrusion 11 is formed to be 5 μm or more and 15 μm or less, and the aspect ratio b / a of the first protrusion 11 is about 1.0 to 1.5. When the size of the first protrusion 11 is optimized, an optimal optical path for incident light can be secured.

That is, incident light is incident and reflected several times through the inclined surfaces SP1 of the plurality of first protrusions 11. Therefore, when the size of the first protrusion 11 is optimized, the light path of the incident light is lengthened to allow more light to enter the inside of the substrate 110.

In addition, as illustrated in FIG. 2C, the angle θ between the inclined surface SP1 and the bottom surface BP of the first protrusion 11 may be formed to be 45 ° or more and less than 54.7 °.

When the surface of the crystalline semiconductor substrate 110 is textured by a general method, the angle θ between the inclined surface SP1 and the bottom surface BP of the first protrusion 11 is 54.7 °.

However, in the present invention, in addition to the anisotropic etching, which is a texturing method that is generally performed, isotropic etching is performed once more to form the first protrusion 11. By doing in this way, the angle (theta) between the inclined surface SP1 and the bottom surface BP of the 1st protrusion part 11 can be formed smaller than 54.7 degrees.

Here, the angle θ between the inclined surface SP1 and the bottom surface BP may be 45 ° or more so that the inclination of the inclined surface SP1 of the first protrusion 11 is kept to a minimum so that the crystalline semiconductor substrate 110 This is to minimize reflectivity at the incident surface.

In addition, the angle θ between the inclined surface SP1 and the bottom surface BP is less than 54.7 ° so that the inclined surface SP1 of the first protrusion 11 is formed more smoothly so that the upper portion of the first protrusion 11 is formed. This is to make the first dielectric layer 130 formed at the more uniform.

3 and 4, a plurality of second protrusions 111 are positioned on the surface of the first protrusion 11, and a second texturing surface is formed on the surface of the first protrusion 11.

At this time, the size (maximum width and maximum height) of the second protrusion 111 formed on the surface of the first protrusion 11 has a smaller value than the size of the first protrusion 11.

For example, the size of the second protrusion 111 may have a maximum width and a maximum height of several hundred nanometers, for example, about 300 nm to about 600 nm.

When the second protrusion 111 is formed on the surface of the first protrusion 11, an incident area of the substrate 110 is further increased and light reflection is repeatedly performed to increase the amount of light incident on the substrate 110. Done.

As such, the surface of the substrate 110 is formed of a first texturing surface having a plurality of first protrusions 11, and the surface of the first protrusion 11 is of a second texturing surface having a plurality of second protrusions 111. Once formed, the reflectivity of light (eg, average weighted reflectance) in the wavelength range of about 300 nm to 1100 nm, as the surface of substrate 110 has a double texturing surface, is about 1% to 10%. It is formed with a low reflectivity of%.

Hereinafter, the second protrusion 111 will be described in detail.

As described above, a plurality of second protrusions 111 are formed on the surface of the first protrusion 11, and the second protrusions 111 are formed to have a maximum width and maximum height of about 300 nm to about 600 nm.

In the vertical section of the second protrusions 111, the length a1 of the imaginary line connecting the vertices and the length of the straight line connecting the start point SP and the finish point FP of the imaginary line The ratio a / b of b1) is 1.1 to 1.3.

Although FIG. 3 shows measuring the ratio a1 / b1 for nine second protrusions 111, the ratio a1 / b1 is measured for three or more second protrusions 111. This is possible, and for the reliability of the measurement, it is preferable to measure at least five or more second protrusions 111.

According to the experiments of the present inventors, when the ratio a1 / b1 is larger than 1.3, the size of the second protrusions 111, that is, the maximum width and the maximum height are formed to be approximately 500 nm to 1,000 nm, and the second protrusions ( 11) the size of the non-uniform, it can be seen that the overall uniformity is low.

In addition, when the ratio a1 / b1 is smaller than 1.1, the size of the second protrusions 111 may be about 200 nm or less, and the size of the second protrusions 111 may be uniform, indicating that the overall uniformity is excellent. there was.

As described above, in view of the uniformity of the second protrusions 111, the case where the ratio a1 / b1 is smaller than 1.1 is superior to the case where the ratio is greater than 1.3.

However, if the ratio (a1 / b1) is greater than 1.3, the reflectance of light is measured to be 7% or less, while the ratio (a1 / b1) is less than 1.1. It was measured at 10% or more.

As such, the reflectivity of light at the second texturing surface increases and decreases in inverse proportion to the ratio a1 / b1, and the reason why the reflectivity of light is inversely proportional to the ratio a1 / b1 is that ratio (a1 / b1). ) Is closer to 1, the size of the second protrusion 111 is reduced, which is considered to be because the reflectivity of light increases.

As described above, when the ratio a1 / b1 is larger than 1.3, it is inferred that the light reflectivity is low, thereby improving the conversion efficiency of the solar cell. However, if the ratio a1 / b1 is larger than 1.3, the size of the second protrusion 111 is larger and the uniformity is lower than that of the ratio a1 / b1 is smaller than 1.1. Increases.

In addition, the current path increases, and the dead area also increases. Therefore, a large current loss occurs for the above reason, so that it is preferable to form the second texturing surface such that the ratio a1 / b1 is 1.3 or less in order to improve the conversion efficiency.

In addition, when the ratio a1 / b1 is smaller than 1.1, the problem occurring in the second texturing surface when the ratio a1 / b1 is larger than 1.3 may be suppressed, The short-circuit current density Jsc increases as compared to the case where the ratio a1 / b1 is larger than 1.3, which reduces the conversion efficiency.

Therefore, in order to improve the conversion efficiency, it is preferable to form the second texturing surface such that the ratio a1 / b1 is 1.1 or more.

As described above, the second protrusions 111 formed on the second texturing surface have the ratio a1 / b1 included in 1.1 to 1.3, and the size of the second protrusion 12a is 300 nm to 600 nm. It can be seen that it is preferable to form so as to be.

As such, when the ratio a1 / b1 of the second protrusions 111 formed on the second texturing surface is included in 1.1 to 1.3, the second area is about a unit area, for example, an area of 10 μm × 10 μm. The ratio of surface area / real area of the texturing surface falls between 2 and 2.5. In this case, the unit area may be changed.

Here, the surface area is the area including the surface area of the second protrusions 111 formed on the second texturing surface within the unit area (triangle A + B + C + D + E + F + G + H + I + J in FIG. 4). The total area is the projection area (S in FIG. 4) seen from the vertical direction of the substrate surface.

The emitter portion 121 located on the substrate 110 is an impurity portion having a second conductivity type, for example, a p-type conductivity type, which is opposite to the conductivity type of the substrate 110. Thus, a p-n junction is formed with the substrate 110 of the first conductivity type.

In the present embodiment, the sheet resistance value of the emitter portion 121 is 100? / Sq. Or less, preferably about 70 Ω / sq. To about 80 Ω / sq.

Due to the built-in potential difference due to the pn junction between the substrate 110 and the emitter portion 121, electrons in the holes and electrons in the holes, which are generated by light incident on the substrate 110, are moved toward the n-type side. Move and the hole moves toward the p-type. Therefore, when the substrate 110 is n-type and the emitter portion 121 is p-type, the electrons move toward the rear surface of the substrate 110 and the holes move toward the emitter portion 121.

When the emitter portion 121 has a p-type conductivity type, the emitter portion 121 may be formed by doping the substrate 110 with impurities of a trivalent element, and the emitter portion 121 may be formed by ion implantation ( ion-implantation).

The first dielectric layer portion 130 includes a second dielectric layer 131 disposed on the emitter portion 121 and a third dielectric layer 132 positioned on the second dielectric layer 131.

In this example, the second dielectric layer 131 is made of aluminum oxide (Al ₂ O ₃ ), and the third dielectric layer 132 is made of hydrogenated silicon nitride (SiNx: H).

In this example, the thickness of the second dielectric layer 131 made of aluminum oxide (Al ₂ O ₃ ) is 5 nm to 15 nm, the refractive index is 1.1 to 1.6, and the third dielectric layer made of hydrogenated silicon nitride (SiNx: H) The thickness of 132 is 70 nm to 100 nm and the refractive index is 2.0 to 2.2.

In this case, since the refractive index of the second dielectric layer 131 adjacent to the substrate 110 is smaller than the refractive index of the third dielectric layer 132 adjacent to the air, the anti-reflection effect due to the refractive index of the second dielectric layer 131 may be reduced. In order to prevent the reduction, the thickness of the second dielectric layer 131 may be much smaller than the thickness of the third dielectric layer 132.

The second dielectric layer 131 made of aluminum oxide (Al ₂ O ₃ ) is positioned on the front surface of the substrate 110, that is, directly on the emitter portion 121 positioned on the front surface of the substrate 110.

Aluminum oxide (Al ₂ O ₃ ) generally has a negative fixed charge.

Accordingly, holes having positive charges are formed by the second dielectric layer 131 of aluminum oxide (Al ₂ O ₃ ) having a negative fixed charge on the p-type emitter portion 121. The field passivation effect is pulled to the side and the electrons are pushed toward the back side of the substrate 110.

Due to the second dielectric layer 131 of the aluminum oxide (Al ₂ O ₃ ), the amount of holes moving toward the emitter portion 121 is further increased, but the amount of electrons moving toward the emitter portion 121 is decreased, so that the emitter portion is reduced. At 121, the amount of recombination of electrons and holes decreases.

In addition, oxygen (O) contained in the aluminum oxide (Al ₂ O ₃ ) moves toward the surface of the substrate 110 in contact with the second dielectric layer 131, and dangling present on and near the surface of the substrate 110. It performs a surface passivation function that converts defects, such as dangling bonds, into stable bonds.

As such, the second dielectric layer 131 made of aluminum oxide (Al ₂ O ₃ ) is preferably formed by an atomic layer deposition (ALD) method having good step coverage.

As described above, as the first texturing surface as well as the second texturing surface of the substrate 110 are formed, the front surface of the substrate 110 in contact with the second dielectric layer 131 of the first dielectric layer portion 130, namely, The roughness of the surface of the emitter portion 121 is increased than when only the first texturing surface is formed.

Therefore, when the second dielectric layer 131 is formed directly on the emitter portion 121 by using a deposition method such as plasma enhanced chemical vapor deposition (PECVD), the second protrusions may be formed on the plurality of protrusions 11 and 111. Since the dielectric layer 131 is not normally applied, a portion in which the second dielectric layer 131 is not formed on the first texturing surface and the second texturing surface of the substrate 110 is increased.

In this case, the surface passivation effect does not occur in the portion where the second dielectric layer 131 is not formed, thereby increasing the amount of charge lost on the surface of the substrate 110.

However, as in the present embodiment, when the second dielectric layer 131 is formed directly on the emitter portion 121 by the atomic layer stacking method having excellent coating performance, the second dielectric layer 131 is formed on the plurality of protrusions 11 and 111. ) Is normally formed to reduce the portion where the second dielectric layer 131 is not formed on the first texturing surface and the second texturing surface.

Accordingly, as the portion of the second dielectric layer 131 formed on the first texturing surface and the second texturing surface increases, the surface passivation effect using the second dielectric layer 131 is improved to improve the surface of the substrate 110 and the vicinity thereof. Since the amount of charge lost is reduced, the efficiency of the solar cell is improved.

A third dielectric layer 132 made of hydrogenated silicon nitride (SiNx: H) is directly over the second dielectric layer 131 located in front of the substrate 110.

Hydrogen H contained in the third dielectric layer 132 moves toward the surface of the substrate 110 via the second dielectric layer 131 to perform a passivation function on and near the surface of the substrate 110.

Thus, due to the passivation function by the third dielectric layer 132 as well as the second dielectric layer 131, the amount of charge lost by the defects on the surface of the substrate 110 is further reduced.

As such, the first dielectric layer 130 located in front of the substrate 110 may include a second dielectric layer 131 of aluminum oxide (Al ₂ O ₃ ) and a third dielectric layer 132 of hydrogenated silicon nitride (SiNx: H). ), The first dielectric layer 130 has a double anti-reflection film structure.

Therefore, not only the anti-reflection effect of light using the refractive index change of the second dielectric layer 131 and the third dielectric layer 132 but also the field passivation effect by the fixed charge of the second dielectric layer 131, and the second dielectric layer 131 and The surface passivation effect is further obtained by the third dielectric layer 132.

When the thickness of the second dielectric layer 131 that is the aluminum oxide film is about 5 nm or more, the aluminum oxide film is formed more uniformly, and the stable charge of the second dielectric layer 131 is generated, thereby making the field passivation effect by the fixed charge more stable. When the thickness of the second dielectric layer 131 is about 15 nm or less, the manufacturing time of the second dielectric layer 131 without reducing the antireflection effect due to the refractive indices of the second dielectric layer 131 and the third dielectric layer 132. And manufacturing costs are reduced.

In addition, when the thickness of the third dielectric layer 132 which is a hydrogenated silicon nitride film is about 70 nm or more, the third dielectric layer 132 is more uniformly formed, and the surface passivation effect using hydrogen (H) is more stably obtained. When the thickness of the dielectric layer 132 is about 100 nm or less, the reduction of the field passivation effect by the hydrogenated silicon nitride film having a positive fixed charge does not occur and the manufacturing time and manufacturing cost of the third dielectric layer 132 are reduced. do.

The rear electric field unit 172 disposed on the rear surface of the substrate 110 may have a high concentration of impurities of a first conductivity type, for example, an n-type conductivity type, which is the same as the conductivity type of the substrate 110. Doped region 110.

The rear electric field unit 172 is in contact with the plurality of rear electrodes 151 and the plurality of rear busbars 152 disposed on the rear of the substrate 110 and is positioned locally on the substrate 110.

Here, the localization of the rear electric field 172 locally on the substrate 110 means that the rear electric field 172 is located only at the rear of the substrate at a position corresponding to at least one of the rear electrode 151 and the rear busbar 152. It means to be located.

As a result, the rear electric field unit 172 is not positioned between the adjacent rear electrodes 151, between the adjacent rear electrodes 151 and the rear bus bar 152, and between the adjacent rear bus bars 152.

Therefore, a potential barrier is formed due to the difference in the impurity concentration between the first conductive region of the substrate 110 and the backside electric field 172, so that hole movement toward the backside electric field 172, which is the direction of electron movement, is hindered. The electron movement toward the rear electric field 172 becomes easier.

Accordingly, the backside electric field 172 reduces the amount of charge lost due to the recombination of electrons and holes in the backside and the vicinity of the substrate 110 and accelerates the movement of the desired charge (eg, electrons) to the backside electrode 150. Increase the amount of charge transfer to

In addition, since the concentration of impurities is higher than that of the substrate 110, the conductivity of the rear electric field 172 in contact with the rear electrode 150 is greater than that of the substrate 110, and the rear electrode of the rear electric field 172. The charge transfer to 150 is made easier.

The second dielectric layer unit 190 includes a first dielectric layer 191 disposed directly on the rear surface of the substrate 110 and a second dielectric layer 131 located directly on the first dielectric layer 191.

The first dielectric layer 191 is made of hydrogenated silicon nitride (SiNx: H), and the second dielectric layer 131 is made of aluminum oxide (Al ₂ O ₃ ) as described above.

In this case, the first dielectric layer 191 may be made of the same material as the third dielectric layer 132 and may have the same characteristics, for example, the same thickness, film quality, composition, composition (or composition ratio), refractive index, and the like.

Accordingly, the first dielectric layer 191 and the third dielectric layer 132 made of hydrogenated silicon nitride (SiNx: H) may have a thickness of about 70 nm to 100 nm and a refractive index of about 2.0 to 2.2, and may include aluminum oxide. The second dielectric layer 131 made of (Al ₂ O ₃ ) may have a thickness of about 5 nm to 15 nm and a refractive index of about 1.1 to 1.6.

As such, since the first dielectric layer 191 made of hydrogenated silicon nitride (SiNx: H) is positioned on the rear electric field 172 directly above the rear of the substrate 110, the surface passivation function using hydrogen (H) is performed. In this case, the amount of electric charge lost by the defects in the rear surface and the vicinity of the substrate 110 is reduced.

In addition, hydrogenated silicon nitride (SiNx: H) has a positive fixed charge characteristic as opposed to aluminum oxide (Al ₂ O ₃ ).

Thus, when the substrate 110 has an n-type conductivity type, when the first dielectric layer 191 made of hydrogenated silicon nitride is positioned directly on the rear surface of the substrate 110, the substrate 110 moves toward the first dielectric layer 191. Since electrons having a negative charge have a polarity opposite to that of the first dielectric layer 191 having positive charge characteristics, the first dielectric layer 191 may be formed by the positive polarity of the first dielectric layer 191. Is pulled to the side.

Holes that are positive charges having the same polarity as the first dielectric layer 191 are pushed toward the front surface of the substrate 110 opposite to the first dielectric layer 191 by the polarity of the first dielectric layer 191.

As a result, when the first dielectric layer 191 is formed by depositing hydrogenated silicon nitride directly on the rear surface of the n-type substrate 110, the positive electrode may move toward the rear surface of the substrate 110 under the influence of positive fixed charge. The amount of electron movement is further increased, and the amount of recombination of charges generated at the rear surface of the substrate 110 is reduced.

The second dielectric layer 131 made of aluminum oxide (Al ₂ O ₃ ) disposed on the first dielectric layer 191 is hydrogen (H) contained in the first dielectric layer 191 by heat applied when fabricating a solar cell. Is prevented from moving toward the rear electrode portion 150 in the opposite direction without moving toward the substrate 110. As a result, the surface passivation effect of the rear surface of the substrate 110 using hydrogen (H) contained in the first dielectric layer 191 is improved.

As such, the first dielectric layer 191 made of hydrogenated silicon nitride (SiNx: H) and aluminum oxide (Al ₂ O ₃ ) are formed on the rear surface of the substrate 110, such as a double anti-reflection film structure disposed on the front surface of the substrate 110. The double passivation layer structure having the second dielectric layer 131 formed of) is formed, thereby improving the passivation effect formed on the rear surface of the substrate 110.

In this case, the first dielectric layer 191 may be used to prevent the influence of the second dielectric layer 131 having a strong negative charge from adversely affecting the first dielectric layer 191 having a positive fixed charge. The thickness of may be thicker than that of the second dielectric layer 131 disposed on the first dielectric layer 191, and may be thicker than the thickness of the third dielectric layer 132 located on the front surface of the substrate 110.

Therefore, if necessary, the thicknesses of the third dielectric layer 132 disposed on the front surface of the substrate 110 and the first dielectric layer 191 disposed on the rear surface of the substrate 110 may be different from each other. In this case, the third dielectric layer 132 positioned on the front surface of the substrate 110 may have a thickness of about 90 nm, and the first dielectric layer 191 positioned on the rear surface of the substrate 110 may have a thickness of about 100 nm. Can be.

In addition, when light is incident on the rear surface of the substrate 110, since the refractive index increases from the air toward the substrate 110, the amount of reflection of the light incident on the rear surface of the substrate 110 decreases and is incident into the substrate 110. The amount of light is reduced. As such, when light is incident on the backside of the substrate 110, the second dielectric layer portion 190 also functions as an antireflection portion.

The plurality of front electrodes 141 of the front electrode unit 140 are connected to the emitter unit 121, and the plurality of front bus bars 142 are connected to not only the emitter unit 121 but also the plurality of front electrodes 141. have.

Accordingly, the plurality of front electrodes 141 are electrically and physically connected to the emitter unit 121 and are spaced apart from each other and extend in parallel in a predetermined direction. The plurality of front electrodes 141 collect charges, for example, holes moved toward the emitter portion 121.

The plurality of front bus bars 142 are electrically and physically connected to the emitter unit 121 and extend in parallel in a direction crossing the plurality of front electrodes 141.

Each front busbar 142 collects charges moving from the emitter unit 121, that is, carriers (eg, holes) as well as charges collected by a plurality of intersecting front electrodes 141 and moves in a desired direction. Since the width of each front bus bar 142 is greater than the width of each front electrode 141.

In this example, the plurality of front busbars 142 are positioned on the same layer as the plurality of front electrodes 141 and are electrically and physically connected to the corresponding front electrodes 141 at points crossing the front electrodes 141. have.

Accordingly, as shown in FIG. 1, the plurality of front electrodes 141 have a stripe shape extending in the horizontal or vertical direction, and the plurality of front busbars 142 have a stripe shape extending in the vertical or horizontal direction. The front electrode 140 is positioned in a lattice shape on the entire surface of the substrate 110.

The plurality of front busbars 142 are connected to an external device and output the collected charges to the external device.

The front electrode part 140 including the plurality of front electrodes 141 and the plurality of front bus bars 142 is made of at least one conductive material such as silver (Ag).

The plurality of rear electrodes 151 of the rear electrode unit 150 are positioned on the rear electric field unit 172 to directly contact the rear electric field unit 172 and are spaced apart from each other in the same direction as the plurality of front electrodes 141. Is laid out.

In this case, the plurality of rear electrodes 151 extend in the same direction as the plurality of front electrodes 141. The plurality of rear electrodes 151 collects charges, for example, electrons, which are moved toward the rear electric field 172.

The plurality of rear busbars 152 of the rear electrode unit 150 are positioned on the rear electric field unit 172 to be in contact with the rear electric field unit 172 and extend side by side in a direction crossing the plurality of rear electrodes 151. have.

In this case, an extension direction of each rear bus bar 152 is the same as an extension direction of each front bus bar 142, and each rear bus bar 152 is centered with each front bus bar 142 around the substrate 110. Can be placed facing each other.

Each rear busbar 152 also collects the charges (e.g., electrons) collected by the plurality of intersecting rear electrodes 151 and moves them in a desired direction, whereby the width of each rear busbar 152 is determined at each rear surface. It is larger than the width of the electrode 151.

For this reason, the plurality of rear busbars 152 are positioned on the same layer as the plurality of rear electrodes 151 and are electrically and physically connected to the rear electrodes 151 at points where they intersect with the rear electrodes 151. .

Accordingly, the rear electrode part 150 is also positioned in a lattice form on the rear side of the substrate 110 like the front electrode part 140.

The plurality of rear electrodes 151 and the plurality of rear bus bars 152 contain the same conductive material as each of the plurality of front electrodes 141 and the plurality of front bus bars 142, for example, silver (Ag). can do. However, the rear electrode part 150 may be made of a different material from the front electrode part 140, and the plurality of rear electrodes 151 and the plurality of rear bus bars 152 may also be made of different materials.

As such, in the present example, the rear electric field unit 172 is disposed under the plurality of rear electrodes 151 and the plurality of rear busbars 152 along the plurality of rear electrodes 151 and the plurality of rear busbars 152. It is extended.

For this reason, the electric field unit 172 is locally positioned on the rear surface of the substrate 110 and has a lattice shape like the rear electrode unit 150. Therefore, as described above, there is a portion of the rear surface of the substrate 110 in which the rear electric field unit 172 is not located.

In this example, the number of the plurality of front electrodes 141 located on the front surface of the substrate 110 to which light is mainly incident is a plurality of the plurality of front electrodes 141 located on the rear surface of the substrate 110 to which a small amount of light is incident than the front surface of the substrate 110. Is less than the number of rear electrodes 151. Thus, the distance between two adjacent front electrodes 141 is greater than the distance between two adjacent rear electrodes 151.

As described above, since the front electrode 140 and the rear electrode 150 contain a metal material such as silver (Ag), a portion where the front electrode 140 and the rear electrode 150 is located Light is not transmitted

Therefore, since the distance between the front electrode 141 located on the front surface of the substrate 110 that receives more light than the rear surface of the substrate 110 increases than the distance between the rear electrode 151, a plurality of the front surface of the substrate 110 The front electrode 141 reduces the size at which the incident surface of light decreases, thereby increasing the amount of light incident on the front surface of the substrate 110.

In an alternative example, at least one of the plurality of front busbars 142 and the plurality of rear busbars 152 may be omitted.

In this example, at least one of the front electrode 140 and the rear electrode 150 may be formed by a plating method.

Therefore, when at least one of the front electrode portion 140 and the rear electrode portion 150 is manufactured by the plating method, at least one of the front electrode portion 140 and the rear electrode portion 150 manufactured by the plating method is the same as the present example. It may be made of a single film, but may be made of a multilayer such as a double film or a triple film. In the case of a single layer, at least one of the front electrode 140 and the rear electrode 150 may be made of silver (Ag).

When at least one of the front electrode portion 140 and the rear electrode portion 150 manufactured by the plating method has a double film structure, the emitter portion 121, that is, is in contact with the portion of the second conductive type of the substrate 110 or the back side The lower layer (first layer) that is in contact with the electric field part 172, that is, the portion of the substrate 110 doped with a high concentration of impurities of the first conductivity type, may be made of nickel (Ni) and disposed on the lower layer. The upper layer (second layer) may be made of silver (Ag).

In addition, when at least one of the front electrode 140 and the rear electrode 150 manufactured by the plating method has a triple film structure, the lower layer contacting the emitter unit 121 or the rear electric field unit 172 (first Film) may be made of nickel (Ni), the intermediate film (second film) located on the lower film is made of copper (Cu), and the upper film (third film) located on the intermediate film is silver (Ag) or tin (Sn). It may be made of.

In this case, when at least one of the front electrode 140 and the rear electrode 150 manufactured by the plating method is a double layer, the thickness of the lower layer may be about 0.5 μm to about 1 μm and the upper layer is about 5 μm to about 10 May be μm.

When at least one of the front electrode 140 and the rear electrode 150 manufactured by the plating method is a triple layer, the thickness of each of the lower layer and the upper layer may be about 0.5 μm to about 1 μm, and the intermediate layer may be about 5 μm to about 10 μm.

At this time, the lower layer is to improve the contact characteristics by reducing the contact resistance with the emitter unit 121 or the back electric field unit 172 is in contact, the intermediate layer is to reduce the cost and good conductivity such as copper (Cu) It may be made of a material having.

When the interlayer is made of copper (Cu), the lower layer under the interlayer is infiltrated into the emitter portion 121 or the rear electric field portion 172 made of silicon (Si) having good bonding force with the silicon (Si). Absorption) to prevent them from acting as impurities that impede the movement of charge.

In addition, the upper film is intended to prevent oxidation of a film (eg, a lower film or an intermediate film) disposed below and to improve adhesion to a conductive film such as a ribbon located on the upper film.

As such, at least one of the front electrode 140 and the rear electrode 150 is formed of a double film or a triple film by a plating method, and when nickel (Ni) is used as a lower film, the nickel (Ni) and the emitter part ( Silicon (Si) of 121, i.e., a combination of silicon of the second conductive type portion of the substrate 110 or nickel (Ni) and silicon of the back surface field portion 172, i.e., impurities of the first conductive type Nickel silicide is present between the lower layer and the emitter portion 121 or between the lower layer and the backside electric field portion 172 by bonding the silicon of the portion of the substrate 110 heavily doped.

On the other hand, at least one of the front electrode 140 and the rear electrode 150 by using a screen printing method using the silver paste (Ag paste) or aluminum paste (Al paste) containing a glass frit (glass frit) When formed, the glass frit penetrates through the first dielectric layer portion 130 or the second dielectric layer portion 190 to be in contact with the emitter portion 121 or the rear electric field portion 172.

Accordingly, at least one of the components of the glass frit, for example, PbO, may be formed at a portion where the front electrode 140 and the emitter portion 121 contact or a portion where the rear electrode 150 and the rear electric field portion 172 contact each other. Bi-based materials such as Pb-based materials, Bi-based materials such as Bi ₂ O ₃ , Al-based materials such as Al ₂ O ₃ , Boron-based materials such as B ₂ O ₃ , Tin (Sn ), At least one of a zinc (Zn) based material such as ZnO, a titanium (Ti) based material such as TiO, and a phosphorous (P) based material such as P ₂ O ₅ is detected.

However, when at least one of the front electrode 140 and the rear electrode 150 is formed by the plating method, the front electrode 141 and the front bus bar 142 and the substrate 110 (that is, the emitter portion 121). ], And components of the glass frit are not detected between the rear electrode 151 and the rear busbar 152 and the substrate 110 (that is, the rear electric field 172).

As described above, when at least one of the front electrode 140 and the rear electrode 150 is formed of a multilayer film, a multilayer film having a desired thickness is sequentially formed by using a plating method from a lower film to an upper film.

In FIG. 1, the number of front electrodes 141, the number of front bus bars 142, the number of rear electrodes 151, and the number of rear bus bars 152 are only one example. In some cases, it can be changed.

The front busbar 142 and the rear busbar 152 collect charges from the emitter part 121 and the rear electric field part 172 as well as the charges collected by the plurality of front electrodes 141, respectively. The charge collected by the rear electrode 151 is collected and output to an external device.

Thus, in an alternative example, at least one of the front busbar 142 and the rear busbar 152 may be located directly above at least one of the first dielectric layer portion 130 and the second dielectric layer portion 190 so as to place the first dielectric layer portion. It may be in contact with at least one of the 130 and the second dielectric layer portion 190.

As already described, the front and back surfaces of the substrate 110 have first and second texturing surfaces, thereby increasing the surface area of the substrate 110.

Therefore, since the area of the emitter portion 121 in contact with each front electrode 141 and the area of the rear electric field portion 172 in contact with each rear electrode 151 increase, each front electrode 141 and each rear electrode 151 are increased. Even if the widths W11 and W12 are reduced, the contact area between the emitter unit 121 and the front electrode 141 and the contact area between the rear electric field unit 172 and the rear electrode 151 are not reduced.

Therefore, even if the widths of the front electrode 141 and the rear electrode 151 decrease, the amount of charge that moves from the emitter unit 121 to each front electrode 141 and the rear electric field 172 to each rear electrode 151 are reduced. The amount of charge moved does not decrease.

In the present embodiment, the width W11 of each front electrode 141 and the width W12 of each back electrode 151 may be about 40 μm to 50 μm, respectively.

As a result, the formation area of the front electrode 141 and the rear electrode 151 that prevents the light from entering the front and rear of the substrate 110 is reduced, and thus the substrate 110 is moved from the front and rear of the substrate 110 to the substrate 110. The amount of incident light increases.

However, due to the first texturing surface and the second texturing surface of the front and rear surfaces of the substrate 110, the emitter portion 121 and the rear electric field portion (eg) to move to the adjacent front electrode 141 and the rear electrode 151. The moving distance of the charges respectively moving along the surface of 172 is increased.

Therefore, in the present embodiment, in order to compensate for the movement distance of the increased charge due to the increase in the surface area of the emitter portion 121 and the increase in the surface area of the rear electric field portion 172, the distance D11 between two adjacent front electrodes 141 is adjacent to each other. It is desirable to reduce the distance D12 between the two rear electrodes 151.

Thus, as an example, the distance D11 between two adjacent front electrodes 141 and the distance D12 between two adjacent rear electrodes 151 may each be about 1.5 mm or more and less than 2.0 mm.

As described above, as the widths W11 and W12 of the respective front electrodes 141 and the rear electrodes 151 decrease, the front and rear surfaces of the substrate 110 may increase even if the distances D11 and D12 between adjacent electrodes increase. The incident area of light does not decrease.

Operation of the solar cell according to the present embodiment having such a structure is as follows.

When light is irradiated onto the solar cell and incident on the substrate 110 through at least one of the first dielectric layer portion 130 and the second dielectric layer portion 190, electron-hole pairs are generated in the substrate 110 by light energy. .

At this time, the reflection loss of light incident on the substrate 110 by the first texturing surface and the second texturing surface of the substrate 110 and the first dielectric layer portion 130 and the second dielectric layer portion 190 is reduced, thereby reducing the substrate 110. ) The amount of light incident on the light increases.

These electrons and holes are formed by the pn junction between the substrate 110 and the emitter portion 121 to form a semiconductor portion having an n-type conductivity, for example, a semiconductor portion having a substrate 110 and a p-type conductivity, For example, they move toward the emitter part 121, respectively.

Holes moved toward the emitter part 121 are collected by the plurality of adjacent front electrodes 141 and the plurality of front busbars 142, move along the plurality of front busbars 142, and move toward the substrate 110. One electron is collected by the plurality of adjacent rear electrodes 151 and the plurality of rear busbars 152 through the rear electric field unit 172 and moves along the plurality of rear busbars 152.

Thus, when the front bus bar 142 of any one solar cell and the rear bus bar 152 of the solar cell adjacent to each other are connected by a conductive wire such as a conductive film, current flows, which is used as power from the outside.

As such, since the front and rear surfaces of the substrate 110 to which light is incident have a double texturing structure, the incident area is increased and the reflection operation due to the plurality of first and second protrusions 11 and 111 is increased. As a result, the amount of light reflected decreases, thereby increasing the amount of light incident into the substrate 110.

In addition to the anti-reflection effect due to the refractive indices of the first dielectric layer 130 and the second dielectric layer 190 located on the front and rear surfaces of the substrate 110, an electric field passivation effect using a fixed charge and hydrogen (H) or oxygen ( The efficiency of the solar cell is improved by the surface passivation effect using O).

Next, a method of manufacturing a solar cell according to an exemplary embodiment of the present invention will be described with reference to FIGS. 5A to 5F and 6.

First, the substrate 110 is manufactured by slicing a silicon block or ingot with a blade or a multi wire saw, wherein the substrate 110 has a mechanical damage layer ( mechanical damage layer is formed.

Accordingly, in order to prevent deterioration of the characteristics of the solar cell due to the mechanical damage layer, wet etching is performed to remove the mechanical damage layer. In this case, as illustrated in FIG. 5A, a plurality of first surfaces of at least one surface of the substrate 110 are removed. A first texturing surface comprising a protrusion 11 is formed.

The process of forming the first texturing surface will be described in more detail with reference to FIG. 6. First, as in step S1 of FIG. 6, the substrate 110 is prepared, and at least one surface of the substrate 110 is anisotropically etched. .

The anisotropic etching is performed by wet etching using an alkaline etching solution, and potassium hydroxide (KOH) or isopropyl alcohol (IPA) may be used as the alkaline etching solution.

When the anisotropic etching is performed as described above, the surface of the substrate 110 is textured as in step S2 to form a first textured surface including the plurality of first protrusions 11.

Here, the material and the etching time of the alkaline etching solution may be variously determined.

At this time, the peak TP1, the valley VP1, and the corner portion EP2 of the inclined surface SP2 of the first protrusion 11 having a pyramid shape are formed very sharply, respectively, and the inclined surface SP2 and the bottom surface thereof. An angle θ1 formed by BP is formed to be 54.7 ° by the characteristics of the crystalline semiconductor substrate 110.

After the step S2, isotropic etching is performed using an acid etchant to further perform wet etching to etch back the plurality of first protrusions.

At this time, as an acid etchant, an etchant containing 0.1 L of hydrogen fluoride (HF), 0.6 L of nitric acid (HNO ₃ ), and 10.2 L of ultrapure water (DI) was used. The first protrusion 11 is etched at an etching speed.

When such isotropic etching is performed, the corner portion EP1 of the inclined surface SP1 of the first protrusion 11 is gradually etched so that the height of the peak TP1 of the first protrusion 11 is gradually lowered. 1 The angle formed between the inclined surface SP1 and the bottom surface BP of the protrusion 11 is reduced to 54.7 degrees or less.

At this time, by adjusting the time of the isotropic etching may be such that the angle between the base surface (BP) has an angle between 45 ° and less than 54.7 °.

By such isotropic etching, the peak TP1 of the first protrusion 11, the corner portion EP1 and the valley VP1 of the inclined surface SP1 are formed into a curved surface.

In this case, the diameters R1, R2, and R3 of the curved portion EP1, the peak TP1, and the valley VP1 of the inclined surface SP1 of the first protrusion 11 adjust the execution time of the isotropic etching. Therefore, it can be made into 5 nm or more and 15 nm or less.

According to the double wet etching process, each of the first protrusions 11 is formed to have a size of 5 μm to 15 μm.

Thereafter, as in step S4, a second texturing surface having a plurality of second protrusions 111 is formed on the surface of the first protrusion 11 by using a dry etching method such as reactive ion etching (RIE). Form.

In this case, the second protrusions 111 are each formed in a size of 200 nm to about 600 nm, and the length a of the imaginary line connecting the vertices and the starting point and the end point of the imaginary line in the vertical section of the second protrusions 111. It is distributed on the surface of the first protrusion 11 so that the ratio (a / b) of the length (b) of the straight line connecting these is 1.1 to 1.3.

In this example, the etching gas used for the reactive ion etching method may be a mixed gas of SF ₆ and Cl ₂ .

After forming the second texturing surface, a process may be further performed to remove residues remaining on the surface of the substrate 110.

In this case, instead of using a separate process chamber, residues may be removed using a dry gas (ie, dry etching) in a process chamber that forms a second texturing surface, in which case, a manufacturing time may be higher than that of using a wet etching method. This is shortened.

In addition, when the residue is removed using the wet etching method, the uneven shape of the first texturing surface and the second texturing surface is changed, but when the residue is removed using the dry etching method, the first texturing surface and The uneven shape of the second texturing surface and the like are maintained. Thus, no change in reflectivity of light by the first texturing surface and the second texturing surface occurs.

In the above description, the first protrusion 11 is formed by isotropic etching using an acid etchant after anisotropic etching using an alkaline etchant, but the AM solution is used as a post-treatment process instead of performing an isotropic etching using an acid etchant. Can be applied.

AM solutions are used in cleaning processes to remove organics, which include treating the substrate with sonic for 5 minutes in acetone and then sonicating for 5 minutes in methanol. can do.

FIG. 7 measures the lifetime of a hydrogenated silicon nitride film according to a method of forming a first texturing surface.

In FIG. 7, Comparative Example 1 illustrates a case where the first texturing surface is formed only by a wet process using an acid etchant, and Comparative Example 2 illustrates a case where the first texturing surface is formed only by a wet process using an alkaline etchant.

Example 1 shows a case in which the first texturing surface is formed by a wet process using an acid etchant after a wet process using an alkali etchant, and Example 2 shows a first texturing surface by applying an AM solution after a wet process using an alkaline etchant. The case where it is formed is shown.

As shown in FIG. 7, when the first texturing surface is formed according to Examples 1 and 2, the life time of the hydrogenated silicon nitride film can be increased compared to Comparative Example 2, and is similar to that of Comparative Example 1. It can be seen that they have a life time.

As such, after the first texturing surface and the second texturing surface are formed on the surface of the substrate 110, as shown in FIG. 5C, a corresponding conductivity type is formed by using an ion implantation method on the entire surface of the substrate 110. And ions of a first impurity having a second conductivity type (for example, p-type) (hereinafter referred to as 'first impurity ions').

In this case, the conductivity type may be the second conductivity type opposite to that of the substrate 110, and the first impurity used in the present example may be boron (B). Therefore, the first impurity ion may be a positive ion (B +) of boron (B).

Accordingly, the first impurity ions having the second conductivity type are implanted into the entire surface of the exposed substrate 110, so that the first impurity portion, which is an impurity portion of the second conductivity type (eg, p-type), is formed on the entire surface of the substrate 110. 120) is formed.

Then, the second impurity ions (hereinafter referred to as 'second impurity ions') having a corresponding conductivity type (ie, first conductivity type) (eg, n-type) are again formed on the rear surface of the substrate 110 by using ion implantation. ) Is implanted to form a second impurity portion 170 on the back surface of the substrate 110.

The second impurity used in the present example may be phosphorus (P), whereby the second impurity ion may be a positive ion (P +) of phosphorus (P).

In this case, in the ion implantation process for forming the first impurity portion 120 and the second impurity portion 170, a mask for implanting the ion may be used only on a desired portion of the front and rear surfaces of the substrate 110.

For example, the mask disposed on the front surface of the substrate 110 blocks only the edge portion of the front surface of the substrate 110 and exposes the remaining portion of the front surface of the substrate 110, and the mask disposed on the rear surface of the substrate 110 The edge portion of the rear surface of the substrate 110, the rear electrode and the rear busbar region may be blocked, and the remaining portion of the rear surface of the substrate 110 may be exposed.

The ion implantation energy for implanting the first impurity ions and the second impurity ions into the substrate 110 may be about 1 keV to 20 keV, and the ion implantation depth may be determined according to the magnitude of the ion implantation energy.

Therefore, the magnitude of the ion implantation energy for the first impurity portion 120 and the magnitude of the ion implantation energy of the second impurity portion 170 may be different from each other.

As an example, the magnitude of ion implantation energy for injecting p-type impurity ions into the substrate 110 may be greater than the magnitude of ion implantation energy for injecting n-type impurity ions into the substrate 110.

In this case, the order in which the first impurity portion 120 and the second impurity portion 170 are formed may be changed, and the first impurity portion 120 and the second impurity portion 170 may be formed in the same chamber, respectively. Each may be formed in a separate chamber.

As such, after the first impurity portion 120 and the second impurity portion 170 are formed, the substrate 110 is heat-treated in a nitrogen (N ₂ ) atmosphere or an oxygen atmosphere (O ₂ ).

As a result, the first impurity portion 120 and the second impurity portion 170 are completely activated. Accordingly, the first impurity portion 120 is formed of an emitter portion 121 positioned on the front surface of the substrate 110 to form a pn junction with the substrate 110, and the second impurity portion 170 is formed of the substrate 110. It is formed of a rear electric field unit 172 located at the rear

That is, the p-type impurity ions and the n-type impurity ions respectively implanted into the substrate 110 form the first impurity portion 120 and the second impurity portion 170 in an interstitial state. When the activation process is performed, the impurity ions in the invasive state are changed into a substitutional state, whereby the rearrangement of silicon, p-type and n-type impurity ions is performed, and the first impurity portion 120 is formed. And the second impurity portion 170 function as the p-type emitter portion 121 and the n-type rear electric field portion 172, respectively.

In this case, boron (B) injected to form the emitter portion 121 is less solubility (solubility) than phosphorus (P) injected to form the back field portion 172, the first impurity portion 120 In order to activate stably, the activation temperature of the first impurity part 120 and the second impurity parts 120 and 170 may be determined based on the first impurity part 120.

Thus, in this example, the activation temperature for the first impurity portion 120 and the second impurity portion 170 may be a temperature at which the first impurity portion 120 is stably activated, for example, about 1000 ° C. to 2000 ° C. , Heat treatment time may be about 20 minutes to 60 minutes.

As described above, since the activation process is performed at a high temperature of about 1000 ° C. or higher at which the boron (B) is stably activated, not only the second impurity portion 170 but also the first impurity portion 120 is stably activated to emitter parts ( 121 and the rear electric field 172 is effectively formed.

In addition, when the heat treatment process is performed at about 1000 ° C. or more, the damaged part generated during the ion implantation process for the first impurity part 120 and the second impurity part 170 is recrystallized to separate the damaged part using a wet etching method or the like. Even without the removal process, the damage caused by ion implantation is healed.

In addition, when the second texturing surface is formed by reactive ion etching, a damaged portion is generated on the surface of the substrate 110 due to the plasma generated during the process.

However, as described above, since the damaged portion is healed by the recrystallization phenomenon of silicon (Si) by a heat treatment process of about 1000 ° C. or more, a separate damaged portion removal process such as a separate wet etching method is also unnecessary.

Therefore, the residue removal process that can be performed after the first texturing surface and the second texturing surface are formed can be omitted, and the damaged portions formed on the surface of the substrate 110 (or the emitter portion 121) are healed and the emi The reflectance of the short wavelength band incident on the detector 121 does not increase.

Next, as shown in FIG. 5E, a first dielectric layer 191 made of hydrogenated silicon nitride (SiNx: H) is formed on the rear surface of the substrate 110.

In this case, the first dielectric layer 191 may be formed through a film deposition process such as plasma enhanced chemical vapor deposition (PECVD). In this example, the thickness of the first dielectric layer 191 may be 70 nm to 100 nm.

Then, as shown in FIG. 5F, a second layer of aluminum oxide (Al ₂ O ₃ ) is formed on the emitter portion 121, which is the front surface of the substrate 110, and on the first dielectric layer 191 positioned on the rear surface of the substrate 110. The dielectric layer 131 is formed.

In this case, the second dielectric layer 131 may be formed using plasma vapor deposition, in particular, atomic layer deposition (ALD).

When the second dielectric layer 131 is formed by the plasma vapor deposition method, since the film is deposited only on the portion exposed by the process gas, the second dielectric layer 131 made of aluminum oxide may be formed using a separate plasma vapor deposition process. It may be formed on the front and rear of the 110, respectively.

In this case, the second dielectric layers 131 positioned on the front and rear surfaces of the substrate 110 may be formed under the same process conditions to have the same film characteristics, or may be formed under different process conditions to have different film characteristics. .

However, when the second dielectric layer 131 is formed using the atomic layer deposition method, the second dielectric layer may be formed not only on the front surface of the substrate 110 but also on the rear surface and the side surface in one stacking process.

Accordingly, the second dielectric layer 131 may be simultaneously formed on the front and rear surfaces of the substrate 110 through one atomic layer deposition method. In this case, since the second dielectric layers 131 respectively positioned on the front and rear surfaces of the substrate 110 are formed under the same process conditions, they have the same film characteristics.

In this example, the thickness of the second dielectric layer 131 may be 5 nm to 15 nm.

When the second dielectric layer 131 is formed, a second dielectric layer portion 190 including the first dielectric layer 191 and the second dielectric layer 131 is formed on the rear surface of the substrate 110.

Next, as shown in FIG. 5G, the third dielectric layer 132 made of silicon nitride (SiNx: H) is formed on the second dielectric layer 131 on the front surface of the substrate by using a plasma vapor deposition method. Form to thickness.

Accordingly, the first dielectric layer part 130 including the second dielectric layer 131 and the third dielectric layer 132 is formed on the front surface of the substrate.

As such, after forming the first dielectric layer portion 130 on the front surface of the substrate 110 and the second dielectric layer portion 190 on the back surface of the substrate 110, the first dielectric layer portion 130 is formed therethrough. A front electrode portion 140 including a plurality of front electrodes 141 and a plurality of front busbars 142 formed in contact with the emitter portion 121 disposed below is formed and penetrated through the second dielectric layer portion 190. A rear electrode 150 formed of a plurality of rear electrodes 151 and a plurality of rear busbars 152 in contact with the rear electric field 172 is formed.

An example for forming the front electrode 140 and the back electrode 150 is as shown in FIG. 5H.

For example, the plurality of first openings 181 and the first openings 181 and the first electrodes 181 are formed at positions where the front electrode 140 and the rear electrode 150 are formed by selectively irradiating a laser beam on the front and rear surfaces of the substrate 110, respectively. Two openings 182 are formed.

In this case, the plurality of first openings 181 penetrate the first dielectric layer part 130 to expose the emitter part 121 positioned below the first dielectric layer part 130, and the plurality of second openings 182 may be formed. The back electric field part 172 disposed under the second dielectric layer part 190 is exposed through the second dielectric layer part 190.

The plurality of first openings 181 are openings for the plurality of front electrodes 141 and the plurality of front busbars 142, and the widths of the first openings 181 for each of the front electrodes 141 are each It is smaller than the width of the first opening 181 for the front busbar 142.

In addition, the plurality of second openings 182 are openings for the plurality of rear electrodes 151 and the plurality of rear busbars 152, and at this time, the widths of the second openings 182 for the respective rear electrodes 151 are provided. Is smaller than the width of the second opening 182 for each rear busbar 152.

In this case, the number of the plurality of first openings 181 for the plurality of front electrodes 141 may be smaller than the number of the plurality of second openings 182 for the plurality of rear electrodes 151. An interval between two first openings 181 may be greater than an interval between two adjacent second openings 182.

In addition, the position at which the first opening 181 is formed for the front bus bar 142 and the position at which the second opening 181 is formed for the rear bus bar 152 may face each other with respect to the substrate 110. .

Then, the plurality of front electrodes 141 and the plurality of front busbars 142 using the plating method such as electroplating or electroless plating on the emitter part 121 exposed through the plurality of first openings 181. And a plurality of rear electrodes 151 and a plurality of rear bus bars 152 on the rear electric field 172 exposed through the plurality of second openings 182. The rear electrode 150 is formed.

In an alternative example, the plurality of front electrodes 141 and the plurality of front busbars 142, and the plurality of rear electrodes 151 and the plurality of rear busbars 152 contain a metallic material such as silver (Ag). One metal paste may be formed by applying a screen printing method to the first opening 181 and the second opening 182 by heat treatment at a desired temperature.

In another alternative example, the plurality of front electrodes 141 and the plurality of front busbars 142, and the plurality of rear electrodes 151 and the plurality of rear busbars 152 may be silver (Ag), or silver ( A metal paste containing a metal material including Ag) and aluminum (Al) may be formed on the first dielectric layer portion 130 and the second dielectric layer portion 190, respectively, followed by drying and heat treatment.

In this case, the plurality of front electrode portions 140 must penetrate the first dielectric layer portion 130, and the plurality of rear electrode portions 150 must penetrate the second dielectric layer portion 190.

Therefore, the metal paste may contain a material (eg, PbO) for etching the first dielectric layer 130 and the second dielectric layer 190. In this case, the amount and type of the etching material included in the metal paste may be determined according to the thickness or material of the first dielectric layer 130 and the second dielectric layer 190.

Therefore, when the metal paste pattern is applied and dried on the first dielectric layer 130 and the second dielectric layer 190, the metal paste penetrates the first dielectric layer 130 and the second dielectric layer 190. Accordingly, a chemical coupling between the emitter unit 121 and the rear electric field unit 172 is performed, and the front electrode unit 140 and the electric field unit 172 electrically and physically connected to the emitter unit 121 are electrically and physically connected to the rear side. The electrode unit 150 is formed.

When at least one of the first dielectric layer part 130 and the second dielectric layer part 190 is omitted, the metal paste forms an electrode part that does not require the penetrating operation of the first dielectric layer part 130 and the second dielectric layer part 190. May not contain an etching material or may contain only an etching material that does not affect the penetration of the dielectric layer portions 130 and 190.

Next, a solar cell according to another embodiment of the present invention will be described with reference to FIG. 8.

In describing the present embodiment, the same components as those of the solar cell of FIG. 1 are given the same reference numerals and detailed description thereof will be omitted.

In comparison with the solar cell shown in FIG. 8 and the solar cell shown in FIG. 8, the solar cell shown in FIG. 8 includes silicon oxide (SiOx) in which the first dielectric layer 130 and the second dielectric layer 190 are hydrogenated. There is a difference in further including a silicon oxide film made of H).

Referring to FIG. 8, the first dielectric layer 130a disposed on the front surface of the substrate 110 may include a second dielectric layer 131 made of aluminum oxide (Al ₂ O ₃ ) and hydrogenated silicon nitride (SiNx: H). In addition to the third dielectric layer 132, a hydrogenated silicon oxide layer 133 disposed directly on the third dielectric layer 132 and made of hydrogenated silicon oxide (SiO x: H) is further provided. For this reason, the first dielectric layer portion 130a has a triple layer 131 to 133 structure.

In addition, the second dielectric layer 190a disposed on the rear surface of the substrate 110 may include a first dielectric layer 191 made of silicon nitride (SiNx: H) and a second dielectric layer 132 made of aluminum oxide (Al ₂ O ₃ ). In the meantime, a hydrogenated silicon oxide film 133 made of hydrogenated silicon oxide (SiOx: H) is further provided. Accordingly, the second dielectric layer part 190a also has a triple layer 191, 133, and 131 structures.

As such, the hydrogenated silicon oxide layer 133 positioned directly on the third dielectric layer 132 and the first dielectric layer 191 may exist in the third dielectric layer 132 and the first dielectric layer 191 disposed below the surface to passivate the surface. The hydrogen (H) for performing the movement is prevented from moving to the opposite side of the substrate (110).

Accordingly, the hydrogenated silicon oxide film 133 positioned in the first dielectric layer 130a and the second dielectric layer 190a respectively caps the third dielectric layer 132 and the first dielectric layer 191 disposed thereunder. It plays a role.

In addition, the hydrogenated silicon oxide film 133 contains hydrogen (H) for curing defects. For this reason, the hydrogenated silicon oxide film 133 performs a function that the hydrogen (H) contained therein passivates the surface of the substrate 110.

Therefore, the passivation effect of the surface of the substrate is further improved by the hydrogenated silicon oxide film 133 positioned on the front and rear surfaces of the substrate 110, respectively.

The hydrogenated silicon oxide film 133 may be formed using a plasma vapor deposition (PECVD) method.

For example, a first dielectric layer 191 made of hydrogenated silicon nitride (SiNx: H) is formed on the back surface of the substrate 110 by plasma vapor deposition, and then hydrogenated silicon oxide (SiOx: H) is formed thereon. The hydrogenated silicon oxide film 133 is formed by plasma vapor deposition, and a _second layer of aluminum oxide (Al ₂ O ₃ ) is formed on the hydrogenated silicon oxide film 133 and directly on the emitter portion 121 located on the front surface of the substrate 110. The dielectric layer 131 is simultaneously formed by atomic layer deposition (ALD), and is sequentially made of silicon nitride (SiNx: H) on the second dielectric layer 131 located on the front surface of the substrate 110 by plasma vapor deposition. A hydrogenated silicon oxide film 133 formed of three dielectric layers 132 and hydrogenated silicon oxide (SiOx: H) is formed.

Except for the method and order of forming the first dielectric layer portion 130a and the second dielectric layer portion 190a, the solar cell manufacturing method of the present embodiment is the same as the solar cell manufacturing method shown in FIGS. 5A to 5F.

The hydrogenated silicon oxide layer 133 made of hydrogenated silicon oxide (SiOx: H) may have a thickness of about 50 nm to about 100 nm, and may have a refractive index of about 1.5.

As described above, the third dielectric layer 132 and the first dielectric layer 191, which are hydrogenated silicon nitride films, are respectively capped by the hydrogenated silicon oxide film 133, so that the passivation function performed by these films is improved, and the hydrogenated silicon is further improved. The passivation effect of the solar cell shown in FIG. 8 is improved by the passivation function performed by the oxide film 133.

In addition, as the hydrogenated silicon oxide layer 133 is added to the first dielectric layer 130a and the second dielectric layer 190a, respectively, the antireflection effect is improved on the front and rear surfaces of the substrate 110. ) The amount of light incident on the light increases. As a result, the current Jsc output from the solar cell increases.

Hereinafter, a solar cell according to still another embodiment of the present invention will be described with reference to FIGS. 9 and 10.

FIG. 9 is another embodiment of the solar cell shown in FIG. 1, and FIG. 10 is another embodiment of the solar cell shown in FIG.

The solar cells shown in FIGS. 9 and 10, respectively, are disposed between the emitter portion 121 and the first dielectric layer portions 130 and 130a and the substrate 110 as compared to the solar cells shown in FIGS. 1 and 5, respectively. A silicon oxide film 180 made of silicon oxide (SiOx) is further provided between the rear surface and the first dielectric layer 191.

Except for the silicon oxide film 180, the solar cells shown in FIGS. 9 and 10 have the same structure as the solar cells shown in FIGS. 1 and 5, respectively.

Accordingly, the silicon oxide film 180 is positioned on the emitter portion 121, which is directly above the front surface of the substrate 110, and directly on the rear surface of the substrate 110, and the first dielectric layer portions 130 and 130a are disposed directly on the silicon oxide film 180. Second dielectric layer portions 190 and 190a are positioned, respectively.

The silicon oxide layer 180 is a chemical oxide layer formed by precipitating the substrate 110 in a desired chemical liquid, and may have a thickness of about 2 nm to 3 nm.

The silicon oxide layer 180 may be formed in the solar cell manufacturing method illustrated in FIGS. 5A through 5F, after the emitter portion 121 is formed, but before the first dielectric layer portion 130 and the second dielectric layer portion 190 are formed. Is formed.

The silicon oxide layer 180 is formed by precipitating the substrate 110 in nitric acid (NHO ₃ ) having a Ph concentration of about 2 to 4 at a process temperature of about room temperature to about 70 ° C. for about 5 to 30 minutes. At this time, the water-containing nitric acid concentration of (NHO _3), that is, content of nitric acid (NHO ₃₎ contained in the water may be from about 65% to 70%.

Generally, during the process of forming the first dielectric layer portions 130 and 130a and the second dielectric layer portions 190 and 190a on the emitter portion 121, the oxygen generated in the air or in the process chamber immediately above the emitter portion 121 is formed. A natural oxide layer is formed.

However, when a film such as aluminum oxide film (Al ₂ O ₃ ) is formed on the natural oxide film, hydrogen (H) contained in the process material for forming the film is combined with the natural oxide film having an unstable bond to water (H ₂ O). Since the hydrogen molecules are formed by forming or hydrogen (H), a problem such as a blistering phenomenon occurs.

However, as in the present example, if the silicon oxide film 180 is formed directly on the front and rear surfaces of the substrate 110 by using a separate chemical vapor deposition method, the occurrence frequency of the problem caused by the combination of oxygen and hydrogen is reduced.

In addition, a passivation function is performed in which the oxygen present in the silicon oxide film 180 changes the bond present on the surface of the substrate 110 into a stable bond, thereby further improving the passivation effect.

In FIGS. 9 and 10, the silicon oxide layer 180 is formed not only on the front surface of the substrate 110 but also on the rear surface of the substrate 110. In an alternative example, only one of the front surface and the rear surface 110 of the substrate 110 may be formed. Can be formed.

As described above, since the silicon oxide film 180 is to improve the surface passivation effect on the front and rear surfaces of the substrate 110 and to reduce the problems caused by the natural oxide film, as described above, the thickness of the silicon oxide film 180 is The thickness is about 2 nm to 3 nm is sufficient without needing to be thick.

 In the present exemplary embodiment, a bifacial solar cell in which light is incident on not only the front surface but also the rear surface of the substrate 110 has been described with reference to the present invention. However, the present invention is not limited thereto. .

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, It belongs to the scope of right.

Claims (24)

A substrate having a first conductivity type;
An emitter portion disposed on the first surface of the substrate and having a second conductivity type;
A first dielectric layer portion located over the emitter portion;
A second dielectric layer portion disposed on the rear surface of the substrate;
A first electrode part connected to the emitter part; And
A second electrode part connected to the substrate
Including;
The emitter portion having a first texturing surface comprising a plurality of first protrusions and a second texturing surface located on the surface of the first protrusion and including a plurality of second protrusions of a smaller size than the first protrusion; ,
And the second protrusion is also located at a peak of at least one of the first protrusions of the plurality of first protrusions. In claim 1,
And the second protrusion is also located in a valley of at least one of the first protrusions of the plurality of first protrusions. 3. The method according to claim 1 or 2,
Each of the first protrusions has a size of 5 μm to 15 μm, and each of the second protrusions has a size of 200 nm to about 600 nm. 4. The method of claim 3,
The size includes a maximum width and a maximum height of each of the first protrusion and the second protrusion. 4. The method of claim 3,
The ratio (a / b) of the length (a) of the imaginary line connecting the vertices and the length (b) of the straight line connecting the starting point and the end point of the imaginary line in the vertical cross section of the second protrusions is 1.1 to 1.3. The method of claim 5,
The ratio (a / b) is a solar cell consisting of the value measured for the three or more second protrusions. 4. The method of claim 3,
The second dielectric layer portion includes a first dielectric layer positioned on the backside of the substrate and a second dielectric layer positioned on the first dielectric layer, wherein the first dielectric layer portion is positioned on the emitter portion and the second dielectric layer A solar cell comprising a third dielectric layer positioned over the dielectric layer. In claim 7,
Wherein the first dielectric layer and the third dielectric layer are each made of hydrogenated silicon nitride having a thickness of 70 nm to 100 nm, and the second dielectric layer is made of aluminum oxide having a thickness of 5 nm to 15 nm. 9. The method of claim 8,
The second dielectric layer portion further includes a hydrogenated silicon oxide film positioned between the first dielectric layer and the second dielectric layer, wherein the hydrogenated silicon oxide film has a thickness of 50nm to 100nm. 9. The method of claim 8,
And a silicon oxide film disposed between the second surface of the substrate and the first dielectric layer, wherein the silicon oxide film has a thickness of 2 nm to 3 nm. 9. The method of claim 8,
The first texturing surface and the second texturing surface are formed on both the first side of the substrate and the second side of the substrate, and light is incident through the first side and the second side of the substrate, respectively. Solar cells. 9. The method of claim 8,
And a hydrogenated silicon oxide film disposed on the third dielectric layer, wherein the hydrogenated silicon oxide film has a thickness of 50 nm to 100 nm. 9. The method of claim 8,
And a silicon oxide film disposed between the emitter portion and the second dielectric layer, wherein the silicon oxide film has a thickness of 2 nm to 3 nm. Performing an anisotropic etching using an alkali etchant to form a first texturing surface comprising at least one first protrusion on at least one side of the substrate;
Performing isotropic etching using an acid etchant to etch back the plurality of first protrusions to form at least one of a peak and a valley of the first protrusion as a curved surface;
Performing a dry etching process to form a second texturing surface on the surface of the first protrusion, the second texturing surface comprising a plurality of second protrusions formed in a smaller size than the first protrusion; And
Performing an ion implantation process to implant impurity ions into the first texturing surface and the second texturing surface, and performing an activation process to form an emitter portion
Including;
And forming the second protrusion even at a peak of at least one first protrusion among the plurality of first protrusions. The method of claim 14,
And a second protrusion formed in a valley of at least one first protrusion of the plurality of first protrusions. The method of claim 14 or 15,
A method of manufacturing a solar cell performing the dry etching process using reactive ion etching (RIE). 17. The method of claim 16,
Forming both the first texturing surface and the second texturing surface on a first surface of the substrate and on a second surface opposite to the first surface, and forming the emitter portion on the first surface of the substrate, The solar cell manufacturing method of forming a rear electric field locally on the second surface of the substrate. The method of claim 17,
The emitter part is formed by implanting and activating a first impurity ion, and the rear field part is formed by implanting and activating a second impurity ion having a conductivity opposite to that of the first impurity ion, and the first impurity ion and the first agent. 2 The impurity ion activation process is performed for 20 to 60 minutes at a temperature of 1000 ℃ to 2000 ℃ the first impurity ion is activated. The method of claim 18,
The solar cell manufacturing method of removing the first surface and the second surface of the substrate damaged by the dry etching process using the activation process. The method of claim 17,
Forming a first dielectric layer on a second side of the substrate;
Simultaneously forming a second dielectric layer over the emitter portion and over a first dielectric layer located on a second side of the substrate;
Forming a third dielectric layer over the second dielectric layer located over the emitter portion; And
Forming a first electrode part connected to the emitter part and a second electrode part connected to the rear electric field part;
Further comprising the steps of: 20. The method of claim 20,
The first dielectric layer and the third dielectric layer are formed by depositing hydrogenated silicon nitride with a thickness of 70 nm to 100 nm, respectively, and the second dielectric layer is formed by depositing aluminum oxide with a thickness of 5 nm to 15 nm, The aluminum oxide is deposited using an atomic layer deposition method. 22. The method of claim 21,
Depositing a hydrogenated silicon oxide in a thickness of 50 nm to 100 nm between the first dielectric layer and the second dielectric layer and over the third dielectric layer. 22. The method of claim 21,
Before forming the first dielectric layer, further comprising the step of immersing the substrate in nitric acid having a Ph concentration of 2 to 4 for 5 to 30 minutes to form a silicon oxide film with a thickness of 2 nm to 3 nm Method of preparation. The method of claim 17,
And the rear electric field part is formed in the same pattern as the plurality of finger electrodes of the second electrode part.

Images