KR101642153B1 - Solar cell and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a solar cell, wherein the solar cell has a first conductive type substrate having a textured surface with a plurality of projections and a plurality of via holes, a second conductive type opposite to the first conductive type, A plurality of first electrodes located on a first side of the substrate and connected to the emitter, a second electrode located on a second side of the substrate opposite the first side of the substrate, A plurality of first electrode current collectors connected to the plurality of first electrodes through the plurality of via holes, and a plurality of first current collectors located on the second surface of the substrate and spaced apart from the plurality of first electrode current collectors And a second electrode connected to the substrate, wherein each of the plurality of first electrodes has a line width of 40 mu m to 80 mu m. As a result, the width of the electrode formed on the surface of the substrate on which the light is incident is reduced to narrow the gap between the electrodes, so that the amount of charge output to the electrode is increased by compensating the movement distance of the charge increased to the textured surface, Thereby improving the efficiency.

Description

SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a solar cell and a manufacturing method thereof.

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 conductive types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types, respectively.

When light is incident on such a solar cell, a plurality of electron-hole pairs are generated in the semiconductor portion, and the generated electron-hole pairs are separated into electrons and holes which are charged by the photovoltaic effect, And the holes move toward the p-type semiconductor portion. The transferred electrons and holes are collected by different electrodes connected to the n-type semiconductor portion and the p-type semiconductor portion, respectively, and electric power is obtained by connecting these electrodes with electric wires.

At this time, in addition to the electrodes, at least one current collector connected to the electrodes is located on the substrate, and the charge collected from the corresponding electrode is output to the external device.

In this case, not only the surface of the substrate on which light is not incident but also the surface on which the light is incident also has the current collecting portion. However, the entire width of the collector is much larger than the width of the electrode, and the incident area of the light is reduced due to the collector, thereby decreasing the efficiency of the solar cell.

Therefore, in order to reduce the efficiency reduction of the solar cell due to the current collectors, solar cells in which a current collector positioned on the incident surface of the substrate is placed on the non-incident surface of the substrate have been developed.

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

A solar cell according to one aspect of the present invention includes a substrate of a first conductivity type having a textured surface having a plurality of via holes and a plurality of projections, a second conductivity type opposite to the first conductivity type, A plurality of first electrodes located on a first surface of the substrate and connected to the emitter section; a second electrode located on a second surface of the substrate opposite to the first surface of the substrate, the plurality A plurality of first electrode current collectors connected to the plurality of first electrodes through a via hole of the substrate, and a plurality of first current collectors located on the second surface of the substrate and spaced apart from the plurality of first electrode current collectors, And each of the plurality of first electrodes has a line width of 40 占 퐉 to 80 占 퐉.

Each of the plurality of first electrodes may have a thickness of 20 占 퐉 to 50 占 퐉.

The maximum diameter and height of each of the plurality of protrusions may be 100 nm to 800 nm, respectively.

The number of the first electrodes may be 100 to 120.

The distance between the center lines parallel to the lengths of the adjacent two first electrodes among the plurality of first electrodes may be 1.3 mm to 1.7 mm.

The aspect ratio of each of the plurality of projections is preferably 1 to 1.5.

The solar cell according to the above feature may further include a plurality of second electrode collectors positioned on the second surface of the substrate and connected to the second electrode.

The first surface of the substrate is an incident surface, and the second surface of the substrate is a non-incident surface.

A method of manufacturing a solar cell according to another aspect of the present invention includes the steps of forming a plurality of via holes in a substrate, forming a texturing surface on a first surface of the substrate having the plurality of via holes, Forming an emitter portion on the substrate; forming an antireflective portion on the first surface of the substrate; forming a plurality of first electrode patterns on the antireflective portion; Forming a plurality of first electrode current collector patterns and a plurality of second electrode current collector patterns on the second surface of the substrate at the same time And heat treating the substrate including the first and second electrode patterns and the plurality of first and second electrode current collector patterns, A plurality of first electrode collectors connected to the plurality of first electrodes, a second electrode connected to the substrate, and a plurality of second electrodes connected to the second electrodes, And forming a collector, wherein each of the plurality of first electrode patterns has a line width of 45 mu m to 85 mu m.

Each of the plurality of first electrode patterns may have a thickness of about 25 mu m to about 55 mu m.

The plurality of first electrode patterns may be formed by at least one of ink jet printing, aerosol jet printing, evaporation, gravure printing, flexo printing, offset printing, Offset printing, gravure offset printing, or the like.

A method of manufacturing a solar cell according to another aspect of the present invention includes the steps of forming a plurality of via holes in a substrate, forming a texturing surface on a first surface of the substrate having the plurality of via holes, Forming an emitter portion on the substrate, forming a plurality of first electrodes on the emitter portion located on the first surface of the substrate, forming a second plurality of electrodes on the second surface of the substrate opposite the first surface, Forming a plurality of first electrode current collector patterns and a plurality of second electrode current collector patterns on the second surface of the substrate at the same time, And a plurality of first electrode current collectors connected to the plurality of first electrodes by heat treatment of the substrate having the plurality of first and second electrode current collector patterns, The second electrode and including a plurality of first forming a collector for the second electrode, the first electrode of the plurality connected with the second electrode has a line width of 40㎛ to 80㎛.

The method of manufacturing a solar cell according to the above feature may further include forming an antireflection portion located on the emitter portion.

The plurality of first electrode forming steps may include removing a part of the anti-reflection part to expose a part of the emitter part, and forming the plurality of first electrodes on the exposed emitter part.

Wherein the step of forming the anti-reflection portion includes the steps of forming a mask on the plurality of first electrodes, forming the anti-reflection portion on the first surface of the substrate, and removing the mask located on the plurality of first electrodes Step < / RTI >

The plurality of first electrodes may be formed by a variety of methods including inkjet printing, aerosol jet printing, evaporation, gravure printing, flexo printing, For example, offset printing, gravure offset printing, or plating.

Each of the plurality of first electrodes may have a thickness of 20 탆 to 50 탆.

And may be formed by screen printing with the first and second electrode current collector patterns and the second electrode pattern.

The textured surface is preferably formed by reactive ion etching.

The textured surface may have a plurality of protrusions, and the maximum diameter and height of each of the plurality of protrusions may be 100 nm to 800 nm, respectively.

The aspect ratio of each of the plurality of protrusions may be 1 to 1.5.

According to this aspect, since the width of the electrode formed on the surface of the substrate on which the light is incident is reduced to narrow the gap between the electrodes, the amount of charge output to the electrode is increased by compensating the movement distance of the charge increased to the textured surface, The efficiency of the solar cell is improved.

1 is a partial perspective view of a solar cell according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the solar cell shown in FIG. 1 taken along line II-II.
3A to 3H are views sequentially illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
4 is a graph showing a change in reflectivity according to the size of each protrusion according to the present embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 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. Also, when a part is formed as "whole" on the other part, it means not only that it is formed on the entire surface (or the front surface) of the other part but also not on the edge part.

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

First, a solar cell according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

Referring to FIGS. 1 and 2, a solar cell 11 according to an embodiment of the present invention includes a substrate 110 having a plurality of via holes 181, A reflection part 130 positioned on the emitter part 121 on an incident surface (hereinafter referred to as a 'front surface') which is a surface of the substrate 110 on which light is incident, an emitter part (Hereinafter, referred to as a 'rear surface'), which is a surface of the substrate 110 positioned opposite to the incident surface without incidence of light, A back surface field (BSF) portion 172, and a second electrode portion 150 positioned on the rear surface of the substrate 110.

The substrate 110 is a semiconductor substrate of a first conductivity type, for example, silicon of p-type conductivity type. The silicon may be monocrystalline silicon, polycrystalline silicon or amorphous silicon. When the substrate 110 has a p-type conductivity type, it contains an impurity of a trivalent element such as boron (B), gallium (Ga), indium (In) or the like. Alternatively, however, the substrate 110 may be of the n-type conductivity type and may be made of a semiconductor material other than silicon. When the substrate 110 has an n-type conductivity type, the substrate 110 may contain impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb), and the like.

The substrate 110 has a plurality of via holes 181 penetrating therethrough and the surface is textured to have a textured surface that is an uneven surface having a plurality of protrusions 21. [ In this embodiment, both the front and back sides of the substrate 110 are textured surfaces, but in an alternative example, only the front side of the substrate 110 may have a textured surface. For convenience, in FIG. 1, only the edge portion of the substrate 110 is shown as a textured surface, and the anti-reflection portion 130 positioned thereon is also shown as an uneven surface only at its edge portion. However, substantially the whole front surface and rear surface of the substrate 110 have a textured surface, so that the antireflective portion 130 located on the front surface of the substrate 110 also has an uneven surface.

In this embodiment, the plurality of projections 21 each have a maximum diameter (a) and height (a) of several hundred nanometers, for example, from about 100 nm to about 800 nm, and more preferably from about 300 nm to about 600 nm b). In this embodiment, the aspect ratio (b / a) of each projection 21 is about 1.0 to 1.5.

As described above, since the size of each protrusion 21 is small as in the case of a nanometer, it is possible to prevent the protrusion 21 from contacting with the air (outside) in each of the protrusions 21 having a sub- ). That is, the upper side of each protrusion 21 has a refractive index close to that of air, and the lower side has a refractive index close to that of silicon (Si), which is a material of the substrate 110, A layer stack effect such as a lamination of a plurality of changing films occurs.

Accordingly, the wavelength range of the light absorbed by the change of the refractive index according to the positional change of each protrusion 21 is also changed, and the wavelength range of the light incident on the substrate 110 is increased. Accordingly, the light reflectance (for example, average weighted reflectance) of the wavelength band in the range of about 300 nm to 1100 nm is detected by the textured surface textured on the surface of the substrate 110 by the dry etching method according to the present embodiment, ] Has a low reflectivity of about 10% or less. As a result, the efficiency of preventing reflection of light of the solar cell 11 due to the textured surface is greatly improved.

More specifically, as shown in FIG. 4, the size of each protrusion 21 varies with the supply amount of chlorine gas (Cl ₂ ) applied to form the textured surface, and the supply amount of chlorine gas (Cl ₂ ) increases The size of each protrusion 21 increases and the maximum diameter and height of each protrusion 21 gradually increases. Conversely, as the supply amount of chlorine gas Cl ₂ decreases, the size of each protrusion 21 decreases, ) Becomes smaller and smaller. Referring to FIG. 4, the supply amount of chlorine gas (Cl ₂ ) when the average weight reflectance is less than about 10% is about 250 sccm to 1600 sccm, and the maximum diameter and height of each protruding portion 21 formed is about 100 Nm to 800 nm. In addition, the supply amount of the chlorine gas (Cl ₂ ) when the average weight reflectance is optimized to 5% or less is about 400 sccm to 1400 sccm, and the maximum diameter and height of each formed protrusion 21 is about 300 nm 600 nm.

When the maximum diameter and height of each protrusion are less than about 100 nm, the textured surface is close to the flat surface, and thus the antireflection effect using the uneven surface can not be effectively obtained. Therefore, when the maximum diameter and height of each projection are about 100 nm or more, the antireflection effect using the uneven surface can be obtained more stably and efficiently. When the maximum diameter and height of each protrusion 21 is greater than about 800 nm, the uniformity of the protrusion 21 formed on the surface of the substrate 110 is lowered, and the time for forming the texturing surface A consumption amount of the process gas such as chlorine gas (Cl ₂ ) increases, and it becomes difficult to control the texturing surface forming process. Therefore, when the maximum diameter and height of each protrusion 21 is about 800 nm or less, a plurality of protrusions 21 are formed more stably and uniformly without unnecessary waste of materials and process time, .

Further, as described with reference to FIG. 4, when the maximum diameter and height of each protrusion 21 is approximately 300 nm to 600 nm, a more preferable antireflection effect is obtained.

The emitter portion 121 formed on the substrate 110 is a region of a second conductive type opposite to the conductive type of the substrate 110, for example, an n-type conductivity type impurity doped to the substrate 110 to be. Thus, the emitter portion 121 of the second conductivity type forms a p-n junction with the first conductive type portion of the substrate 110.

The surface of the substrate 110 is a textured surface having a plurality of projections 21 so that the surface of the emitter portion 121 doped in the substrate 110 is also covered with the projections 21 having a plurality of protrusions 21, The interface between the first conductive type portion of the substrate 110 and the emitter portion 121, that is, the interface between the substrate 110 and the emitter portion 121 (i.e., the pn junction surface) And has an uneven surface similar to the surface of the substrate 110 due to its shape.

Due to the built-in potential difference due to the pn junction, the electron-hole pairs generated by the light incident on the substrate 110 are separated into electrons and holes, electrons move toward the n-type, Moves toward the p-type. Accordingly, when the substrate 110 is p-type and the emitter section 121 is n-type, the separated holes move toward the substrate 110, and the separated electrons move toward the emitter section 121.

Since the emitter section 121 forms a pn junction with the substrate 110, the emitter section 121 has a p-type conductivity type when the substrate 110 has an n-type conductivity type, unlike the present embodiment . In this case, the separated electrons move toward the substrate 110, and the separated holes move toward the emitter 121.

When the emitter section 121 has an n-type conductivity type, the emitter section 121 can be formed by doping an impurity of a pentavalent element into the substrate 110, and conversely, the emitter section 121 can be formed of a p- Type, it can be formed by doping an impurity of a trivalent element into the substrate 110. [

The antireflective portion 130 located on the emitter portion 121 on the front surface of the substrate 110 may be formed of a silicon nitride film (SiNx), a silicon oxide film (SiOx), or the like. The antireflective portion 130 reduces the reflectivity of light incident on the solar cell 11 and increases the selectivity of a specific wavelength region, thereby enhancing the efficiency of the solar cell 11. The anti-reflection portion 130 may have a multi-layer structure such as a single-layer structure or a double-layer structure, and may be omitted as necessary.

The reflection preventing part 130 and the emitter part 121 at the lower part thereof are formed with exposed parts (not shown) for exposing a part of the edge of the front surface of the substrate 110. Therefore, the emitter section 121 formed on the front surface of the substrate 110 and the emitter section 121 formed on the rear surface of the substrate 110 are electrically separated by the exposed section.

The first electrode unit 140 includes a plurality of front electrodes 141 disposed on the front surface of the substrate 110 and a plurality of front electrodes 141 disposed on the rear surface of the substrate 110 through a plurality of via holes 181. [ And a plurality of front electrode current collectors 142 connected to the plurality of electrodes.

A plurality of front electrodes 141 are electrically and physically connected to the emitter section 121 and are spaced apart from each other and extend in a predetermined direction. Therefore, the plurality of front electrodes 141 have a stripe shape extending in the horizontal or vertical direction.

The plurality of front electrodes 141 of the first electrode unit 140 electrically and physically connected to the emitter unit 121 at the front surface of the substrate 110 may cause the plurality of front surfaces And is located on the emitter section 121 where the electrode 141 is not located.

In the present embodiment, each front electrode 141 has a line width w1 of about 40 占 퐉 to 80 占 퐉, a thickness of about 20 占 퐉 to 50 占 퐉, and an interval p1 between adjacent two front electrodes 141 is About 1.3 mm to 1.7 mm. The distance p1 is a distance between the center lines of the front electrodes 141 parallel to the length of the front electrodes 141. [ Accordingly, the total number of the front electrodes 141 formed in one solar cell 11 may be about 100 to 120.

The plurality of front electrodes 141 collects charges, for example, electrons, which have migrated toward the emitter section 121.

It can be seen that the front electrode 141 has a line width much smaller than that of the front electrode disposed in the solar cell of the comparative example having a line width of about 90 μm to 120 μm and a thickness of about 15 μm to 25 μm. In the comparative example, since the linewidth of each front electrode is larger than that of the present embodiment, the number of front electrodes is about 80 times less than that of the present embodiment, and the distance between the center lines of the front electrodes parallel to the length of the front electrodes is about 1.8 mm To 2.3 mm.

Since the distance between the front electrodes 141 is reduced in order to compensate the movement distance of the increased charge due to the textured surface, the movement distance of the charges moving to the adjacent front electrode 141 through the emitter portion 121 is reduced So that the amount of charges transferred from the emitter section 121 to the front electrode 141 greatly increases.

That is, in the case of the present embodiment, since the width and height of the projecting portion 21 formed on the textured surface have nanometer units, the surface area of the textured surface is greatly increased. Generally, electrons move mainly along the surface of the substrate 110, and thus, when the surface area of the textured surface increases, the distance of movement of charge increases greatly.

Therefore, as in the comparative example, when the distance between the front electrodes is large, the charge transfer distance increases greatly due to the surface area increased to the texturing surface, so that charges moving toward the front electrode along the texturing surface are transferred to the dangling bonds, Or other charges, and the amount of charge collected by the front electrode is greatly reduced, thereby decreasing the efficiency of the solar cell. In order to solve this problem, the distance between the front electrodes is reduced to reduce the moving distance of the charges.

However, if the distance between the front electrodes is reduced without reducing the line width of the front electrode, the light receiving area of the solar cell is greatly reduced and the efficiency of the solar cell is reduced.

Accordingly, the present embodiment reduces both the line width w1 of the front electrode 141 and the distance p1 between the front electrode 141 and the front electrode 141. [ Even if the number of the front electrodes 141 increases, the moving distance of the charges moving to the front electrode 141 is reduced without reducing the light receiving area. As a result, the amount of charge collected by the front electrode 141 increases.

At this time, when the line width of the front electrode 141 is reduced only, the wiring resistance of each front electrode 141 is increased, so that the thickness of each front electrode 141 is also increased as compared with the comparative example. Thus, the charges are transferred to the front electrode 141 more stably and efficiently without increasing the wiring resistance due to the reduction of the line width of the front electrodes 141.

When the line width and the thickness of each front electrode 141 are equal to or more than the lower limit value, the front electrode 141 functions more stably. On the other hand, when the front electrode 141 is below the upper limit value, the width of the front electrode 141 increases unnecessarily, Resulting in waste of material. In particular, when the thickness of each front electrode 141 is less than the upper limit value, the front electrode 141 having the corresponding thickness is formed more stably.

The plurality of front electrodes 141 are made of at least one conductive material such as silver (Ag).

The rear electric field portion 172 located on the rear surface of the substrate 110 is a region where a conductive type impurity the same as the substrate 110 is doped into the substrate 110 at a higher concentration than the substrate 110, for example, a P + region.

A potential barrier is formed due to the difference in impurity concentration between the first conductive region and the rear conductive portion 172 of the substrate 110, thereby preventing the electron movement toward the rear conductive portion 172, which is the direction of the movement of the holes , It becomes easier to move the hole toward the rear electric section 172. Accordingly, the rear electric field 172 reduces the amount of electric charge lost due to the recombination of electrons and holes at the back surface of the substrate 110 and the vicinity thereof, accelerates the movement of a desired electric charge (e.g., a hole) 150).

The plurality of front electrode current collectors 142 extend in a direction intersecting the plurality of front electrodes 141 located on the front surface of the substrate 110 on the rear surface of the substrate 110 where the via holes 181 are located. At this time, the plurality of front electrode current collectors 142 are also referred to as bus bars and extend in parallel to each other. Therefore, the plurality of front electrode current collectors 142 have a stripe shape extending in the longitudinal or transverse direction. As shown in Fig. 1, a plurality of via holes 181 are formed in the substrate 110 at a portion where a plurality of front electrodes 141 and a plurality of front electrode current collectors 142 intersect each other. The inside of the corresponding plurality of via holes 181 is filled with at least one of the front electrode 141 and each of the front electrode collectors 142 crossing the plurality of front electrodes 141, The front electrode 141 of the front electrode 141 and the front electrode current collector 142 which intersects with the plurality of front electrodes 141 are electrically and physically connected through the plurality of via holes 181. [

 The number of the front electrode current collectors 142 formed on the solar cell 11 may be two or three, and each front electrode current collector 142 may have a line width of about 1.5 mm.

The plurality of front electrode current collectors 142 collects and collects electric charges collected by the plurality of front electrodes 141 as well as charges (for example, electrons) moving from the portions of the emitter contacts 121 that are in contact with each other. do.

Since the plurality of front electrode current collectors 142 are connected to the external device, the electric charges collected by the plurality of front electrode current collectors 142 are output to the external device.

The second electrode unit 150 includes a rear electrode 151 positioned on the rear surface of the substrate 110 and a plurality of rear electrodes 151 located on the rear surface of the substrate 110 and electrically and physically connected to the rear electrode 151. [ And a current collector 152.

The rear electrode 151 is in contact with the rear electric field 172 located on the rear surface of the substrate 110 and is spaced apart from the adjacent front electrode current collector 142. In the present embodiment, the rear electric section 172 is mainly located on the rear surface of the substrate 110, which is in contact with the rear electrode 151. The rear electrode 151 collects charges, for example, holes, which move toward the substrate 110.

The rear electrode 151 is made of a conductive material such as aluminum (Al).

The emitter section 121 formed between the rear electrode 151 and the plurality of front electrode current collecting sections 142 surrounds the front electrode current collecting sections 142 and exposes a part of the rear surface of the substrate 110 And a plurality of exposed portions 182 are provided.

The electrical connection between the front electrode 142 for collecting electrons or holes and the rear electrode 151 for collecting holes or electrons is broken by the exposed portion 182, so that the movement of electrons and holes is smooth.

The plurality of rear electrode current collectors 152 are spaced apart at regular intervals and have a stripe shape extending in parallel with the plurality of front electrode current collectors 142. The plurality of rear electrode current collectors 152 are electrically and physically connected to the portions of the adjacent rear electrodes 151. [ However, in an alternative example, each of the rear electrode current collectors 152 may include a plurality of conductors arranged at regular intervals in parallel with the adjacent front electrode current collectors 142. At this time, the cross-sectional shape of each conductor may be circular, oval or polygonal.

The plurality of rear electrode current collectors 152 collects charges, for example, holes, which are transferred from the substrate 110 and are transferred from the back electrode 151.

Since the plurality of back electrode current collectors 152 are also connected to the external device, the charges collected by the plurality of back electrode current collectors 152 are output to the external device.

1 and 2, in the alternative example, the plurality of rear electrode current collecting parts 152 are overlapped with a part of the rear electrode 151, and the rear electrode 151 and the plurality of rear electrode current collecting parts 152 Can be increased. As a result, the charge transfer efficiency between the back electrode 151 and the plurality of back electrode current collectors 152 is improved.

The plurality of front electrode current collectors 142 and the plurality of rear electrode current collectors 152 collect the charges collected by the plurality of front electrodes 141 and the rear electrodes 151 and move them in a desired direction It may be made of a material having better conductivity than the front electrode 141 and the rear electrode 151 and may contain at least one conductive material such as silver (Ag), for example. The line width of the plurality of front electrode current collectors 142 and the plurality of rear electrode current collectors 152 may be larger than the line width of the plurality of front electrodes 141 in order to reduce wiring resistance.

1 and 2, a part of the emitter 121 is present on the rear surface of the substrate 110 in contact with the back electrode current collector 152, but is not limited thereto.

The solar cell 11 according to this embodiment having such a structure is a solar cell in which a front electrode current collector 142 connected to the front electrode 141 is disposed on the rear surface of the substrate 110 on which no light is incident , The operation is as follows.

When light is irradiated to the solar cell 11 and enters the semiconductor substrate 110 through the emitter section 121, electron-hole pairs are generated in the semiconductor substrate 110 by light energy. At this time, since the surface of the substrate 110 is a textured surface, the light reflectivity at the front surface of the substrate 110 is reduced, and the incidence and reflection operations are performed at the textured surface to increase the light absorption rate. do. In addition, the reflection loss of light incident on the substrate 110 by the anti-reflection unit 130 is reduced, and the amount of light incident on the substrate 110 is further increased.

These electron-hole pairs are separated from each other by the pn junction of the substrate 110 and the emitter section 121, so that the electrons move toward the emitter section 121 having the n-type conductivity type and the holes become the p- And moves toward the substrate 110 having the first substrate 110. Electrons migrating toward the emitter section 121 are collected by the plurality of front electrodes 141 and moved to the front electrode collector 142 electrically connected through the plurality of via holes 181, Holes are collected by the rear electrode 151 through the rear electric part 172 and moved to the rear electrode current collector 152. [ When the front electrode current collector 142 and the back electrode current collector 152 are connected to each other by a wire, current flows and is used as external power.

At this time, the line width of the front electrode 141 located on the incident surface of the substrate 110 is reduced to increase the number of the front electrodes 141, thereby reducing the interval between the adjacent front electrodes 141. As a result, the distance traveled by the electrons moving from the emitter 121 to the adjacent front electrode 141 is reduced. Therefore, even if the surface area due to the texturing surface increases, the electrons move from the emitter 121 to the front electrode 141 The amount of charge does not decrease. Since the incident surface of the solar cell 11 does not decrease despite the increase in the number of the front electrodes 141 due to the decrease in the line width of the front electrode 141, the efficiency of the solar cell 11 Does not occur. In addition, since the thickness of the front electrode 141 increases, no reduction in wiring resistance occurs.

Since the aspect ratios of the protruding portions 21 of the textured surface are about 1.0 to 1.5, the amount of recombination loss of charge generated on the surface of the substrate 110 and the vicinity thereof and the amount of recombination loss of the surface electrode 141 and the emitter portion 121 And the like. That is, when each of the protrusions 21 has an aspect ratio of about 1.0 or more, the contact thickness of the emitter section 121 contacting the front electrode 141 is stably ensured and the contact margin of the front electrode 141 is increased , The front electrode 141 passes through the emitter section 121 to further reduce the occurrence of defects in shunt contact with the substrate 110 and the height of each protrusion 21 is not too low, The antireflection effect used can be obtained more efficiently and stably. In addition, when the aspect ratio of each protrusion 21 is about 1.5 or less, the doping thickness of the emitter section 121 is prevented from increasing unnecessarily. As a result, It is possible to further prevent the recombination loss of charges due to these inactive impurities on the surface of the substrate 121 and in the vicinity thereof.

Next, a method of manufacturing the solar cell 11 according to an embodiment of the present invention will be described with reference to FIGS. 3A to 3H. FIG.

As shown in FIG. 3A, first, a plurality of via holes 181 are formed in a substrate 110 made of p-type single crystal or polycrystalline silicon. At this time, the via hole 181 is formed by laser drilling which is formed by irradiating a laser beam, but is not limited thereto.

Next, as shown in FIG. 3B, a surface of the exposed substrate 110, for example, a front surface of the substrate 110, which is an incident surface, is etched using a dry etching method such as reactive ion etching (RIE) To form a textured surface having a plurality of protrusions (21). The size of the maximum diameter and height of each protrusion 21 may be, for example, about 100 nm to 800 nm, more preferably about 300 nm to 600 nm, as the submicron, and the aspect ratio of each protrusion 21 May range from about 1 to about 1.5.

Next, as shown in FIG. 3C, a substance including an impurity of a pentavalent element such as phosphorus (P), arsenic (As), antimony (Sb) or the like, for example, POCl ₃ or H ₃ PO ₄ are diffused into the substrate 110 to diffuse the impurity of the pentavalent element to the emitter 121 on the entire surface of the substrate 110, that is, the front surface, the rear surface, the inner surface and the side surface of the via hole 181, . Unlike the present embodiment, when the conductive type of the substrate 110 is n-type, a substance including an impurity of a trivalent element, for example, B ₂ H ₆ , is heat-treated or laminated at a high temperature, a p-type emitter portion can be formed. Then, a phosphorus silicate glass (PSG) or a boron silicate glass (BSG) containing phosphorus, which is generated as the p-type impurity or n-type impurity diffuses into the substrate 110, Lt; / RTI >

Next, as shown in FIG. 3D, an antireflective portion 130 is formed on the entire surface of the substrate 110 by using a chemical vapor deposition (CVD) method such as plasma enhanced chemical vapor deposition (PECVD) . At this time, the anti-reflection portion 130 may be formed in the via hole 181.

Next, as shown in FIG. 3E, a paste for a current collector including silver (Ag) is applied to a corresponding position of the emitter portion 121 on the rear surface of the substrate 110 using a screen printing method, The current collector pattern 42 for the back electrode and the current collector pattern 52 for the back electrode are formed and then dried at about 170 캜.

At this time, the front electrode current collector pattern 42 is formed on the plurality of via holes 181 located on the same line. The front electrode current collector pattern 42 may be formed of a metal such as nickel (Ni), copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium (In) ), Gold (Au), and combinations thereof.

Next, as shown in FIG. 3F, on the emitter portion 121 on the back surface of the substrate 110, except for the portion where the front electrode current collector pattern 42 and the back electrode current collector pattern 52 are formed, Electrode paste is applied to coat the rear electrode pattern 51 and then dried at about 170 캜. At this time, the paste for the rear electrode contains aluminum (Al). Alternatively, silver (Ag), nickel (Ni), copper (Cu), tin (Sn), zinc (Zn), indium Ti), gold (Au), and combinations thereof.

Next, as shown in FIG. 3G, a material containing a conductive material such as silver (Ag) is formed on the antireflective portion 130 located on the front surface of the substrate 110 by inkjet printing, For example, by aerosol jet printing, evaporation, gravure printing, flexo printing, offset printing, or gravure offset printing. A plurality of front electrode patterns 41 having a line width of about 45 μm to 85 μm and a thickness of about 25 μm to 55 μm are formed. At this time, the plurality of front electrode patterns 41 are formed in a direction intersecting the plurality of front electrode current collector patterns 42 at the positions where the plurality of via holes 181 are formed, and the interval between the adjacent two patterns 41 is about 1.3 to 1.7 mm, and the number of the patterns 41 may be about 100 to 120. At this time, since the width and the height of the pattern 41 are contracted by the heat treatment operation of the front electrode pattern 41 to be performed later, the line width and the thickness of the pattern 41 are adjusted to the line width 40 Mu m to 80 mu m) and the thickness (about 20 mu m to 50 mu m).

Generally, when a plurality of front electrode patterns are formed by using a screen printing method, the minimum width and the minimum vertical size of the mesh required to form a mesh of a mask used for screen printing, It is difficult to form a pattern having a line width of any size or less, and it is impossible to reduce the line width of the pattern by a desired size.

However, the surface area of the emitter section 121 has already been increased by the texturing surface, thereby increasing the distance traveled by the charge moving along the surface of the emitter section 121.

In the case of forming the front electrode pattern by the screen printing method, since the line width of each pattern can not be reduced by a desired size, the distance between the adjacent two front electrode patterns is narrowed in order to compensate the movement distance of the increased charge, The area where the light is incident is reduced by the number of the increased front electrode patterns. As a result, the amount of light incident into the substrate 110 decreases and the efficiency of the solar cell 11 decreases.

However, in the present embodiment, in order to reduce the distance between the plurality of front electrode patterns 41 without reducing the incident area, the width of the plurality of front electrode patterns 41 may be reduced, (41) is increased as compared with the prior art. To this end, a plurality of front electrode patterns 41 are formed by using a printing method capable of forming a pattern having a desired line width (about 45 μm to 85 μm) and a desired thickness (about 25 μm to 55 μm).

Particularly, roll printing such as gravure printing, flexographic printing, offset printing, gravure offset printing, and the like allows a desired printing width (about 45 to 85 탆) and a desired thickness 25 占 퐉 to 55 占 퐉) can be formed, so that the formation time of the front electrode pattern 41 is further reduced.

In the present embodiment, the front electrode current collector having a line width that is about 200 to 300 times larger than the line width of each front electrode is positioned on the rear surface of the substrate 110. Accordingly, since only the front electrode having the same size and the same size are formed on the same surface of the substrate 110, it is not necessary to form the front electrode current collector pattern, so that the number of times of printing and the printing time of the front electrode pattern 41 are greatly reduced.

That is, when a plurality of front electrodes and a plurality of front electrode current collectors are all located on the front surface of the substrate 110, the front electrode patterns and the front electrode current collectors are formed using different printing methods, The front electrode pattern and the front electrode current collector must be formed.

Therefore, when the plurality of front electrodes and the plurality of front electrode collectors are all located on the same substrate 110, the process for forming the plurality of front electrodes and the plurality of front electrode collectors becomes very complicated, , The production time of the solar cell is increased and the productivity of the solar cell is decreased.

However, in the present embodiment, a plurality of front electrodes and a plurality of front electrode current collectors are disposed on different surfaces of the substrate 110, respectively. Therefore, it is necessary to form a plurality of front electrodes and a plurality of front electrode current collectors Time does not increase.

A plurality of front electrode current collector patterns 42 and a plurality of front electrode patterns 41 are formed at positions where the via holes 181 of the substrate 110 are formed, At least one of the current collector pattern 42 and the front electrode pattern 41 is located and the corresponding front electrode current collector pattern 42 and the front electrode pattern 41 are connected to each other via the via hole 181. [

The formation order of the rear electrode pattern 51, the front and rear electrode current collector patterns 42 and 52, and the front electrode pattern 41 may be changed.

When the rear electrode pattern 51, the rear electrode pattern 42 and the front electrode pattern 42 and the front electrode pattern 41 are formed on the rear and front surfaces of the substrate 110, A plurality of front electrodes 141 connected to the emitter section 121 and a plurality of front electrodes 141 connected to the plurality of front electrodes 141, A plurality of rear electrode current collectors 152 connected to the rear electrodes 151 and a plurality of rear electrodes 151 connected to the rear electrodes 151. The rear electrode 151 and the rear electrode 151 are electrically connected to each other, A backside electrical portion 172 is formed in the substrate 110 which is in contact with the substrate 151.

 That is, when the heat treatment is performed, the front electrode pattern 41 penetrates through the antireflective portion 130 of the contact portion by the lead (Pb) contained in the front electrode pattern 41, A plurality of front electrode current collectors 142 which are in contact with the plurality of front electrodes 141 and are connected to the plurality of front electrodes 141 via via holes 181, A rear electrode 151 is formed.

3 (h), aluminum (Al) contained in the rear electrode pattern 51 is diffused toward the substrate 110 in contact with the rear electrode pattern 51, and the substrate 110 The rear electric section 172 is formed. At this time, the rear electric section 172 has the same conductivity type as that of the substrate 110, and the impurity concentration of the rear electric section 172 is higher than that of the substrate 110. As a result, the rear electrode 151 connected to the substrate 110 is formed through the rear electric part 172.

Further, due to the heat treatment, the contact resistance between the metal parts contained in the patterns 41, 42, 51, 52 and the layers 121, The flow of charge becomes good.

An exposed portion 182 for exposing a part of the substrate 110 around the current collector 142 for the front electrode is formed by using a laser so that a back electrode 151 electrically connected to the substrate 110, The light collecting part 142 is separated and the reflection preventing part 130 formed at the edge of the front surface of the substrate 110 and the part of the emitter part 121 below the part are removed to expose a part of the front surface of the substrate 110. [ (Not shown) to complete the solar cell 11 (Figs. 1 and 2). Alternatively, the formation of the plurality of exposed portions 182 and the lateral separation may be performed by using a PECVD method instead of the laser.

The front electrode pattern 41 is formed on the antireflection portion 130 and then heat treatment is performed to form a plurality of front electrodes 141 connected to the emitter portion 121.

However, in an alternative example, a part of the antireflective portion 130 may be removed to expose a portion of the emitter portion 121, and then the above-described printing method, electroplating or LIP a plurality of front electrodes 141 may be formed by a plating method such as a light induced plating method. In this case, the plurality of front electrodes 141 may be formed before or after the electrodes 151 and the current collectors 142 and 152 are formed on the rear surface of the substrate 110.

Alternatively, after the formation of the emitter layer 121, a plurality of front electrodes 141 having a line width of about 40 to 80 mu m are formed by the above printing method, plating method, or the like, The anti-reflection portion 131 can be formed only at a desired position on the front surface of the substrate 110. [ That is, after forming the emitter layer 121, a plurality of front electrodes 141 are formed directly on the emitter layer 121 located on the incident surface of the substrate 110, and a mask is formed on the plurality of front electrodes 141 . Then, the anti-reflection part 130 is formed on the incident surface of the substrate 110 again, and then the mask located on the plurality of front electrodes 141 is removed. The reflection preventing portion 130 is located on the emitter portion 121 of the incident surface of the substrate 110 on which the plurality of front electrodes 141 are located. In this case, the plurality of front electrodes 141 may be formed before or after the electrodes 151 and the current collectors 142 and 152 are formed on the rear surface of the substrate 110.

When a plurality of front electrodes 141 are directly formed on the emitter layer 121 by the plating method in order to improve adhesion and conductivity between the emitter layer 121 made of silicon and the plurality of front electrodes 141, A seed layer may be additionally formed by performing a plating or vapor deposition operation using titanium (Ti) and lead (Pb) or the like before performing the plating for the first electrode 141.

When the plurality of front electrodes 141 are formed by the above methods, the operation of penetrating the front end electrode pattern 41 located on the antireflection portion 130 is unnecessary, It is possible to eliminate the heat treatment process for forming the front electrode 141 or lower the temperature of the heat treatment process. Since the penetration operation of the reflection preventing part 130 is not required, the heat treatment temperature for forming the electrodes 151 and the current collectors 142 and 152 located on the rear surface of the substrate 110 is also greatly reduced. Accordingly, damage to other films or components located on the substrate 110 or the substrate 110 due to a high heat treatment for the operation of the reflection preventing part 130 is prevented.

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.

11: solar cell 41: front electrode pattern
42: current collecting portion for front electrode pattern 51: rear electrode pattern
52: current collecting pattern for rear electrode 110:
121: Emitter part 130: Antireflection part
140: first electrode part 141: front electrode
142: front electrode current collector 150: second electrode portion
151: back electrode 152: back electrode current collector
172: rear electric field portion 181: via hole
182:

Claims (21)

A substrate of a first conductivity type having a texturing surface having a plurality of via holes and having a plurality of protrusions,
An emitter portion having a second conductivity type opposite to the first conductivity type and forming a pn junction with the substrate, the emitter portion being located within the first surface of the substrate and within the plurality of via holes,
A plurality of first electrodes located on a first surface of the substrate and connected to the emitter,
A plurality of first electrode current collectors located on a second surface of the substrate opposite to the first surface of the substrate and connected to the plurality of first electrodes and the emitter through the plurality of via holes,
A second electrode located on the second surface of the substrate and spaced apart from the plurality of first electrode current collectors and connected to the substrate,
And a plurality of second electrode current collecting parts located on the second surface of the substrate and connected to the second electrode and the emitter part,
Lt; / RTI >
Wherein each of the plurality of first electrodes has a line width of 40 mu m to 80 mu m,
Wherein the doping concentration of the emitter portion located on the first surface of the substrate and the doping concentration of the emitter portion located inside the plurality of via holes are the same. The method of claim 1,
Wherein each of the plurality of first electrodes has a thickness of 20 占 퐉 to 50 占 퐉. The method of claim 1,
And a maximum diameter and a height of each of the plurality of projections is 100 nm to 800 nm, respectively. 4. The method according to any one of claims 1 to 3,
Wherein the number of the plurality of first electrodes is 100 to 120. 4. The method according to any one of claims 1 to 3,
Wherein a distance between center lines parallel to a length of two adjacent first electrodes among the plurality of first electrodes is 1.3 mm to 1.7 mm. 4. The method according to any one of claims 1 to 3,
And each of the plurality of protrusions has an aspect ratio of 1 to 1.5. delete The method of claim 1,
Wherein the first surface of the substrate is an incident surface and the second surface of the substrate is a non-incident surface. Forming a plurality of via holes in the substrate,
Forming a textured surface on a first side of the substrate having the plurality of via holes,
Forming a first surface of the substrate and a second surface opposite to the first surface, and forming an emitter portion in the plurality of via holes;
Forming an anti-reflective portion on the first side of the substrate,
Forming a second electrode pattern on the second surface of the substrate using screen printing;
Simultaneously forming a plurality of first electrode current collector patterns and a plurality of second electrode current collector pattern on the second surface of the substrate using a screen printing method,
Forming a plurality of first electrode patterns on the antireflection portion, and
The method comprising: heat-treating the substrate including the plurality of first electrode patterns, the second electrode pattern, and the plurality of first and second electrode current collector patterns to form the emitter portion and the firing portion located on the first surface of the substrate, A plurality of first electrodes connected to the plurality of first electrodes, a second electrode connected to the second surface of the substrate, and a plurality of second electrodes connected to the plurality of first electrodes by a fire-through operation, Forming a second electrode and a plurality of second electrode current collectors connected to the emitter portion of the second surface;
Lt; / RTI >
Wherein each of the plurality of first electrode patterns has a line width of 45 mu m to 85 mu m,
The first electrode pattern is formed by a method different from the first and second electrode current collector patterns,
Wherein the doping concentration of the emitter portion located on the first surface of the substrate and the doping concentration of the emitter portion located inside the plurality of via holes are equal to each other. The method of claim 9,
Wherein each of the plurality of first electrode patterns has a thickness of about 25 占 퐉 to about 55 占 퐉. The method according to claim 9 or 10,
The plurality of first electrode patterns may be formed by at least one of ink jet printing, aerosol jet printing, evaporation, gravure printing, flexo printing, offset printing, Wherein the photoresist is formed by an offset printing method or a gravure offset printing method. Forming a plurality of via holes in the substrate,
Forming a textured surface on a first side of the substrate having the plurality of via holes,
Forming a first surface of the substrate having the texturing surface and a second surface opposite the first surface, and forming an emitter portion within the plurality of via holes;
Forming a second electrode pattern on the second surface of the substrate using screen printing;
Simultaneously forming a plurality of first electrode current collector patterns and a plurality of second electrode current collector pattern on the second surface of the substrate using a screen printing method,
Forming a plurality of first electrode patterns on the emitter portion located on the first surface of the substrate, and
The substrate including the plurality of first electrode patterns, the second electrode pattern, and the plurality of first and second electrode current collector patterns is subjected to heat treatment to connect the emitter section on the first surface of the substrate A plurality of first current collectors connected to the plurality of first electrodes, a second electrode connected to the second surface of the substrate, and a second electrode connected to the second electrode and the second surface, Forming a plurality of second electrode current collectors connected to the tabs;
Lt; / RTI >
Wherein the plurality of first electrodes have a line width of from 40 탆 to 80 탆,
The first electrode pattern is formed by a method different from the first and second electrode current collector patterns,
Wherein the doping concentration of the emitter portion located on the first surface of the substrate and the doping concentration of the emitter portion located inside the plurality of via holes are equal to each other. The method of claim 12,
And forming an antireflection portion on the emitter portion. The method of claim 13,
The plurality of first electrode pattern forming steps may include removing a portion of the anti-reflection portion to expose a portion of the emitter portion, and
Forming the plurality of first electrode patterns on the exposed emitter layer
Wherein the method comprises the steps of: The method of claim 13,
The forming of the anti-reflection portion may include forming a mask on the plurality of first electrode patterns,
Forming the antireflective portion on the first side of the substrate, and
Removing the mask located on the plurality of first electrode patterns
Wherein the method comprises the steps of: The method of claim 12,
The plurality of first electrode patterns may be formed by at least one of ink jet printing, aerosol jet printing, evaporation, gravure printing, flexo printing, offset printing, A method of manufacturing a solar cell, which is formed by an offset printing method, a gravure offset printing method, or a plating method. The method of claim 12,
Wherein each of the plurality of first electrodes has a thickness of 20 占 퐉 to 50 占 퐉. delete 13. The method according to claim 9 or 12,
Wherein the textured surface is formed by a reactive ion etching method. 13. The method according to claim 9 or 12,
Wherein the textured surface has a plurality of protrusions, and each of the plurality of protrusions has a maximum diameter and a height of 100 nm to 800 nm, respectively. . 20. The method of claim 19,
Wherein the aspect ratio of each of the plurality of protrusions is 1 to 1.5.

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