KR101544216B1

KR101544216B1 - Solar cell and method for manufacturing the same

Info

Publication number: KR101544216B1
Application number: KR1020090083655A
Authority: KR
Inventors: 고지훈; 강주완; 김종환; 장대희
Original assignee: 엘지전자 주식회사
Priority date: 2009-09-04
Filing date: 2009-09-04
Publication date: 2015-08-12
Also published as: KR20110025543A

Abstract

A solar cell according to an embodiment of the present invention includes a substrate having a plurality of via holes, an emitter section, a plurality of first electrodes electrically connected to the emitter section, a plurality of first electrodes electrically connected to the substrate, A plurality of second electrodes, and a separator in which a part of the substrate is exposed. The first electrode includes a front portion located on a front surface of the substrate and a rear portion connected to the front portion through a via hole and located on a rear surface of the substrate. The separating portion includes a first separating portion for electrically insulating adjacent front portions from each other and a second separating portion for electrically insulating the rear portion and the adjoining second electrodes in one direction. At this time, the rear portion is electrically connected to the adjacent second electrode in the other direction.

MWT, solar cell, via hole, separator,

Description

SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME

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

With the recent depletion of existing energy resources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells generate electric energy from solar energy, and they are environmentally friendly and have an advantage of long life as well as infinite solar energy.

Solar cells are divided into silicon solar cell, compound semiconductor solar cell and tandem solar cell according to the raw material, and silicon solar cell is mainstream.

A typical silicon solar cell has a substrate and an emitter layer made of semiconductors having different conductive types such as p-type and n-type, and electrodes formed on the substrate and the emitter, respectively. At this time, a p-n junction is formed at the interface between the substrate and the emitter.

When sunlight enters the solar cell, electrons and holes are generated in a silicon semiconductor doped with an n-type or p-type impurity by a photovoltaic effect. For example, electrons are generated in a majority carrier in an n-type emitter portion made of an n-type silicon semiconductor, and holes are generated in a majority carrier in a p-type substrate made of a p-type silicon semiconductor. Electrons and electrons, which are carriers generated by the photovoltaic effect, are attracted toward the substrate, which is an n-type semiconductor emitter and a p-type semiconductor, respectively, and are moved to electrodes electrically connected to the substrate and the emitter, respectively. Power is obtained.

At this time, at least one bus bar connected to the emitter and the electrode formed on the semiconductor substrate is placed on each of the emitter and the semiconductor substrate, and the carrier collected from the electrode is connected to the load connected to the outside through the adjacent bus bar So that it can be easily moved.

However, in this case, since the bus bar is located not only on the semiconductor substrate where no light is incident but also on the emitter portion where the light is incident, the incidence area of the light is reduced due to the bus bus, thereby reducing the efficiency of the solar cell.

A metal wrap through (MWT) solar cell has been developed to reduce the efficiency of the solar cell due to the bus bar, in which a bus bar connected to the emitter is positioned on a semiconductor substrate where no light is incident.

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

A solar cell according to the present invention includes a substrate having a plurality of via holes, an emitter section, a plurality of first electrodes electrically connected to the emitter section, a plurality of second electrodes electrically connected to the substrate, An electrode, and a separation portion in which a part of the substrate is exposed. The first electrode includes a front portion located on a front surface of the substrate and a rear portion connected to the front portion through a via hole and located on a rear surface of the substrate. The separating portion includes a first separating portion for electrically insulating adjacent front portions from each other and a second separating portion for electrically insulating the rear portion and the adjoining second electrodes in one direction. At this time, the rear portion is electrically connected to the adjacent second electrode in the other direction.

According to this feature, a plurality of solar cells are formed on one substrate, so that a solar cell having a small volume and a high voltage can be obtained.

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. Like parts are designated with like reference numerals throughout the specification. 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 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, 2A, and 2B.

1 is a partial cross-sectional view of a solar cell according to an embodiment of the present invention.

FIG. 2A is a cross-sectional view of the solar cell of FIG. 1 cut along a line II-II, and FIG. 2B is an equivalent circuit of a solar cell showing current flow of FIG. 2A.

Referring to FIG. 1, a solar cell 1 according to an embodiment of the present invention includes a substrate 110 of a first conductivity type having a plurality of via holes A, 110 and an emitter layer 120 of a second conductivity type opposite to the first conductive type.

The solar cell 1 further includes an antireflection coating layer disposed on the emitter 120 formed on a substrate 110 (hereinafter referred to as a front portion) (130).

The solar cell 1 includes a plurality of first electrodes 140 positioned on the emitter section 120 formed on the substrate 110 where the antireflection film 130 is not disposed and electrically connected to the emitter section, And a plurality of second electrodes 150 disposed on a substrate 110 (hereinafter, referred to as a 'rear portion') facing the front without light incident thereon and electrically connected to the substrate, .

The first electrode 140 is connected to the front part 141 through the via hole A and the rear part 142 located on a part of the rear surface of the substrate, .

The solar cell 1 further includes a first separator 181 for electrically insulating the adjacent front portions 141 from each other and a second separator 183 for electrically insulating the rear portion 142 and the adjacent second electrode 150 in one direction. And a second separator 182 that separates the first and second separators.

The solar cell 1 is disposed between each second electrode 150 and the lower substrate 110 and has a plurality of back surfaces of a first conductivity type having a higher impurity concentration than the substrate field, BSF) unit 160. [0033]

A potential barrier is formed due to a difference in impurity concentration between the substrate 110 and the rear electric field portion 160 and the movement of holes toward the rear surface of the substrate 110 is obstructed so that electrons and holes recombine at the rear surface of the substrate 110, .

The substrate 110 is a semiconductor substrate made of silicon of the first conductivity type, for example, 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, indium, or the like.

Alternatively, the substrate 110 may have an 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 A penetrating therethrough, and the surface of the substrate 110 has a texturing surface which is an uneven surface.

The emitter portion 120 is an impurity portion having a second conductivity type opposite to the conductivity type of the substrate 110, for example, an n-type conductivity type, and forms a p-n junction with the semiconductor substrate 110.

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

When the substrate 110 is p-type and the emitter 120 is n-type, the separated holes move toward the substrate 110 and the separated electrons move toward the emitter 120, And the electrons in the emitter section 120 become a majority carrier.

Since the emitter layer 120 forms a p-n junction with the substrate 110, the emitter layer 120 has a p-type conductivity when the substrate 110 has an n-type conductivity, unlike the present embodiment. In this case, the separated electrons move toward the substrate 110 and the separated holes move toward the emitter part 120.

When the emitter section 120 has an n-type conductivity type, an impurity of a pentavalent element such as phosphorus (P), arsenic (As), antimony (Sb) or the like is doped into the semiconductor substrate 110, 120 may be formed. Conversely, when a p-type conductive type is employed, impurities of a trivalent element such as boron (B), gallium, indium, etc. may be doped into the substrate 110.

Referring to FIG. 2A, the emitter section 120 is formed to extend to the front surface of the substrate and the inner surface of the via hole A to a part of the rear surface of the substrate.

An antireflection film 130 made of silicon nitride (SiNx), silicon oxide (SiO ₂ ), or the like is formed on the emitter portion 120 on the front surface of the substrate 110. The antireflection film 130 lowers the reflectivity of light incident on the solar cell 1, thereby enhancing the efficiency of the solar cell 1. In an alternative embodiment, the antireflection film 130 may also be located on the side wall of the via hole A. [ The antireflection film 130 may be omitted if necessary.

Meanwhile, the front portion 141 of the first electrode and the rear portion 142 of the first electrode are made of at least one conductive material. Examples of these conductive metal materials include metals such as Ni, Cu, Ag, Al, Sn, Zn, In, Ti, ), And combinations thereof, but may be made of other conductive metal materials.

In this embodiment, it is preferable that the front electrode 141 of the first electrode and the rear electrode 142 of the first electrode are made of the same material.

The plurality of second electrodes 150 are formed of at least one conductive material. The conductive material may be at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, And combinations thereof, but may be made of other conductive metal materials.

The front portions 141 of the plurality of first electrodes are spaced apart from each other at a predetermined interval on the emitter portion 120 formed on the entire surface of the substrate and cover the via hole A penetrating the substrate.

1, adjacent first electrode portions 141 are spaced apart from each other, and are electrically connected to each other by a first separator portion 181 in which a part of the emitter portion is removed between adjacent first electrode portions 141 As shown in Fig.

The electrical connection between the emitter part 120 for moving and collecting electrons (or holes) by the first separator 181 and the front part 140 of the first electrode is cut off and the movement of electrons .

2A, it is preferable that the first separator 181 is adjacent to the beginning of the via hole A in the front surface of the substrate, that is, the edge of the via hole A, in consideration of the efficiency of charge collection Do. For the same reason, the optimum depth h of the first separator 181 is in the range of 10 탆 to 20 탆 with respect to the horizontal plane of the front surface of the substrate, and the interval L between the front portions 141 of the adjacent first electrodes Is preferably substantially the same as the width w of the first separator 181. [ At this time, since the first separator 181 is formed using a laser, the width of the first separator 181 is in the range of 10 μm to 20 μm.

The rear portion 142 of the first electrode is located on the inner wall of the via hole A and a part of the rear surface of the substrate 110. The interface of the back surface portion 142 and the emitter portion 120 in the via hole A are in contact with each other.

The rear portion 142, also referred to as a bus bar, has a shape extending substantially parallel to the second electrode 150 in a direction intersecting with the front portion 141 located at the upper portion.

The front portion 141 of the first electrode and the rear portion 142 of the first electrode are electrically connected to each other while being in direct surface contact. Accordingly, the front surface 141 of the first electrode collects a carrier, for example, electrons, which has migrated toward the emitter section 120, and transfers the carrier to the rear portion 142 of the first electrode through the via hole A. The rear portion 142 of each first electrode outputs a carrier, for example, electrons, transmitted from the front portion 141 of the first electrode to an external device.

In this embodiment, since the rear portion 142 of the first electrode connected to the front portion 141 of the first electrode is formed on the rear surface of the substrate where no light is incident, .

The plurality of second electrodes 150 collects one of carriers, for example, holes, which have moved toward the semiconductor substrate 110, and outputs the collected carriers to an external device. A conductive material having a good conductivity such as silver (Ag) is attached to a part of each second electrode 150 to improve contact force with an external device.

1, the second electrode 150 extends substantially parallel to the rear portion 142 of the first electrode, and the second electrode 150 and the rear portion 142 of the first electrode are alternately arranged .

The emitter section 120 includes a plurality of second separation sections 182 that expose a part of the rear surface of the substrate. Referring to FIG. 2A, the rear portion 142 of the first electrode is formed between the adjacent second electrodes in one direction (for example, in the left direction with respect to the rear portion of the first electrode in FIG. 2A) 2 separator 182, and is electrically insulated.

On the other hand, the rear portion 142 of the first electrode is in electrical contact with the adjacent second electrode in the other direction (for example, rightward with respect to the rear portion in FIG. 2A).

Therefore, the solar cell according to the present embodiment can be interpreted as a solar cell group in which a plurality of unit solar cells exist in one substrate.

Here, the unit solar cell according to the present embodiment refers to a solar cell including a front surface and a rear surface of a first electrode, a second electrode, and a via hole (A), and capable of generating electric power by itself.

2B, since each unit solar cell is a diode in a circuit, a second electrode for collecting holes, a unit first solar cell, a front portion of the first electrode, a rear portion of the first electrode, a second electrode, A second solar cell, and the like are formed.

At this time, since the plurality of unit solar cells are electrically connected in series with other adjacent unit solar cells through the via holes A formed in the substrate, according to the embodiment of the present invention in which a plurality of solar cells are formed on one substrate The voltage of the solar cell equals the sum of the voltages generated by the unit solar cell.

Therefore, the solar cell according to the present embodiment can obtain a high voltage with a small volume, and thus can be used for auxiliary power of an electronic product such as a cellular phone.

In addition, the current generated in the solar cell is proportional to the area of the solar cell. Therefore, according to the embodiment of the present invention in which a plurality of solar cells are formed on one substrate, the generated current value becomes small, so that the resistance heat is small and the thermal stability is high.

Further, a plurality of unit solar cells are formed on one substrate, and the electrodes are connected directly between the unit solar cells without using a conductor such as a ribbon.

The operation of the solar cell 1 according to this embodiment having such a structure is as follows. When light is irradiated onto the substrate 110 of the semiconductor through the antireflection film 130 and the emitter section 120, electron-hole pairs are generated in the substrate 110 of the semiconductor due to light energy.

These electron-hole pairs are separated from each other by the pn junction of the substrate 110 and the emitter section 120 so that the electrons move toward the emitter section 120 having the n-type conductivity type and the holes become the p- And moves toward the substrate 110 having the first substrate 110. The electrons moved toward the emitter part 120 are collected by the front part 141 of the first electrode and moved to the rear part 142 of the first electrode electrically connected via the via hole A, Are collected and moved by the second electrode 150 through the adjacent rear electric field 160.

As shown in FIG. 2B, since the unit solar cells formed on one substrate are connected to each other in series according to the present embodiment, any one of the unit solar cells located at both ends of the plurality of solar cells formed on one substrate When the first current collector 171 and the second current collector 172, which are electrically connected to the electrode, are connected by a conductor, a current flows and is used as electric power from the outside.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a partial cross-sectional view of a solar cell according to a second embodiment of the present invention, which is different from FIG.

1, 2A, and 2B, the same reference numerals are assigned to those parts that perform the same function, and a detailed description thereof will be omitted.

Referring to FIG. 3, a third separator 183 may be further formed between the rear portion 142 of the second electrode and the adjacent second electrode 150 in the other direction, with a portion of the emitter portion removed. In order to electrically connect the rear portion 142 of the first electrode 150 to the second electrode 150, the second electrode conductive layer 151 is formed of aluminum (Al) Need to be additionally formed.

Therefore, the rear portion 142 of the first electrode and the conductive layer 151 for the second electrode can be electrically connected by using a conductor 173 such as a ribbon.

Next, a second embodiment of the present invention will be described with reference to Figs. 4A and 4B.

4A is a partial cross-sectional view of a solar cell according to a third embodiment of the present invention,

4b is an equivalent circuit of the solar cell showing the current flow of Fig. 4a.

However, unlike the first separator shown in FIGS. 1 and 2A in which a part of the emitter formed between the front portions of the adjacent first electrodes is removed, the solar cell according to the third embodiment of the present invention shown in FIG. A plurality of unit solar cells are cut and electrically insulated, and then electrically connected in series by using a conductor 174 such as a ribbon.

In other words, the first separator 183 shown in FIG. 4A is formed by cutting from the front surface of the substrate between the adjacent first electrodes to the rear surface of the substrate, or by cutting the rear surface 142 of the first electrode as well as the substrate .

In the case where the first separator 183 is formed by cutting the rear surface 142 of the first electrode as well as the substrate, a conductor 174 for electrically connecting the rear surface 142 of the cut first electrode is required When the first separator 183 is formed by cutting only the substrate, the conductor 174 is unnecessary.

In order to manufacture the solar cell 2 according to the third embodiment of FIG. 4, a plurality of via holes A are formed on one substrate 110 of the first conductivity type, Forming a front portion 141 of the first electrode electrically connected to the emitter portion 120 on the front surface of the substrate 110 and forming a front portion 141 of the first electrode electrically connected to the emitter portion 120 on the front surface of the substrate 110, A rear surface portion 142 of the first electrode electrically connected to the emitter portion 120 is formed on the rear surface of the substrate 110 through the via hole A and connected to the front surface portion 141 of the first electrode, And a second separator 182 electrically isolating the second electrode 150 adjacent to the rear face 142 of the first electrode from the first electrode 150. The second electrode 150 is electrically connected to the second electrode 150, And the substrate is cut at a point between the front portions 141 of the adjacent first electrodes. Further, a step of electrically connecting the rear portion 142 of the first electrode to the adjacent second electrode 150 in the other direction may be additionally required.

That is, in order to electrically insulate the adjacent first electrodes in a final manufacturing step of a single substrate on which a via hole is formed, a metal wrap (not shown) is used in that the substrate is cut at a point between the front portions 141 of the first electrodes. through, MWT).

Referring to FIG. 4B, similarly to FIG. 2B, since each unit solar cell is a diode in a circuit, a second electrode for collecting holes, a unit first solar cell, a front portion of the first electrode, A conductor 174 such as a ribbon, a part of the cut rear face portion of the first electrode, a second electrode, a unit second solar cell, and the like are formed.

In this case, since a plurality of unit solar cells are electrically connected in series to other adjacent unit solar cells through the via holes A formed in the substrate, according to the embodiment of the present invention in which a plurality of solar cells are formed on one substrate, The voltage of the solar cell is equal to the sum of the voltages generated by the unit solar cell.

Therefore, the solar cell according to the present embodiment can also be used for an auxiliary power of an electronic product such as a cellular phone, since a high voltage can be obtained with a small volume. In addition, since the current generated in the solar cell is proportional to the area of the solar cell, according to the present embodiment in which a plurality of solar cells are formed on one substrate, the generated current value is small, Is high.

As shown in FIG. 4B, since the unit solar cells formed on one substrate are connected in series to each other according to this embodiment, any one of the unit solar cells located at both ends of the plurality of solar cells formed on one substrate When the first current collector 171 and the second current collector 172, which are electrically connected to the electrode, are connected by a conductor, a current flows and is used as electric power from the outside.

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.

FIG. 4A is a partial cross-sectional view of a solar cell according to another embodiment of the present invention, and FIG. 4B is an equivalent circuit of a solar cell showing current flow in FIG. 4A.

Claims

A first conductive type substrate having a plurality of via holes,

A second conductivity type emitter portion formed on the substrate and opposite to the first conductivity type;

A plurality of first electrodes located on the emitter part formed with the substrate and electrically connected to the emitter part,

A plurality of second electrodes electrically connected to the substrate, and a separation unit disposed on a rear surface of the substrate,

The first electrode includes a front portion located on a front surface of the substrate and a rear portion connected to the front portion via the via hole and located on a rear surface of the substrate,

Wherein the separator includes a first separator for electrically insulating the adjacent front portions from each other and a second separator for electrically insulating the rear portion and the adjacent second electrodes in one direction, And the electrodes are electrically connected to each other.

The method according to claim 1,

Wherein a part of the emitter portion formed between the adjacent front portions is removed from the first separator.

The method according to claim 1,

Wherein the first separator is adjacent to the edge of the via hole in the front surface of the substrate.

The method according to claim 1,

Wherein a distance between front portions of the adjacent first electrodes is substantially equal to a width of the first separator.

The method according to claim 1,

And the width of the first separator is in the range of 10 탆 to 20 탆.

The method according to claim 1,

Wherein a depth of the first separator is 10 占 퐉 to 20 占 퐉 based on a horizontal plane of the front surface of the substrate.

The method according to claim 1,

Wherein a part of the emitter portion formed between the rear portion and the adjacent second electrode of the one direction is removed from the second separator.

The method according to claim 1,

Wherein the emitter portion extends to a portion of the rear surface of the substrate through the front surface of the substrate and the inner wall of the via hole.

The method according to claim 1,

And the adjacent second electrodes are spaced apart from each other.

The method according to claim 1,

Wherein the rear surface portion and the adjacent second electrodes in one direction are spaced apart from each other.

The method according to claim 1,

And the adjacent second electrode in a direction different from the rear surface is formed by direct surface contact.

The method according to claim 1,

And a portion of the emitter portion formed between the adjacent second electrodes in the other direction to the rear portion is removed.

13. The method of claim 12,

A second electrode conductive layer is further formed on the adjacent second electrode in the other direction,

And the rear portion and the conductive layer for the second electrode are electrically connected to each other.

The method according to claim 1,

And an antireflection film disposed on the emitter portion formed on the front surface of the substrate.

The method according to claim 1,

And the interface of the rear portion and the emitter portion in the via hole are in contact with each other.

The method according to claim 1,

And a backside electric field portion of a first conductivity type located between the second electrode and the substrate and having a higher impurity concentration than the substrate.

Forming a plurality of via holes in a substrate of a first conductivity type;

Forming an emitter portion of the second conductivity type opposite to the second conductivity type on the substrate;

A front surface portion of a first electrode electrically connected to the emitter portion is formed on a front surface of the substrate and a rear surface portion of a first electrode electrically connected to the emitter portion is formed on the rear surface of the substrate through the via hole, Forming a plurality of second electrodes electrically connected to the substrate on a rear surface of the substrate,

Forming a second separator for electrically insulating the rear portion and the adjacent second electrodes in one direction, and cutting the substrate at a point between the adjacent front portions.

18. The method of claim 17,

In cutting the substrate,

And the rear portion is cut together.

18. The method of claim 17,

And electrically connecting adjacent second electrodes in a direction different from the rear surface.

A solar cell produced by the method according to any one of claims 17 to 19.