KR101531469B1 - Solar cell - Google Patents

Abstract

The present invention relates to a solar cell. The solar cell according to an example of the present invention comprises a semiconductor substrate containing impurities of a first conductive type; an emitter part containing a second conductive type impurities which is opposite to the first conductive type, and arranged on one side of the semiconductor substrate; a back electroluminescent part containing high concentration impurities of the first conductive type compared with the semiconductor substrate, and arranged on the opposite side of one surface of the semiconductor substrate; a first electrode electrically connected to the emitter part; and a second electrode electrically connected to the back electroluminescent part, and further comprises a first bypass part arranged on a part of an area where the emitter part and the first electrode are overlapped, electrically connected to the first electrode, and containing impurities of the first conductive type opposite to the emitter part, or further comprises a second bypass part located on a part of an area where the back electroluminescent part and the second electrode are overlapped, electrically connected to the second electrode, and containing impurities of the second conductive type opposite to the back electroluminescent part.

Description

Solar cell {SOLAR CELL}

The present invention relates to a solar cell.

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, respectively, so that the electrons move toward the n- 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.

Such solar cells can be connected to each other by an interconnection.

An object of the present invention is to provide a solar cell having a bypass unit.

A solar cell according to an example of the present invention includes: a semiconductor substrate containing an impurity of a first conductivity type; An emitter portion containing an impurity of a second conductivity type opposite to the first conductivity type and disposed on one surface of the semiconductor substrate; A rear electric field portion containing impurities of the first conductivity type at a high concentration than the semiconductor substrate and disposed on the opposite surface of the semiconductor substrate; A first electrode electrically connected to the emitter portion; And a second electrode electrically connected to the back electroluminescent portion, wherein the emitter portion and the first electrode are electrically connected to the first electrode by being positioned at a portion of the overlapping region, Type impurities, or a part of the region where the back electroluminescence portion and the second electrode are overlapped with each other and is electrically connected to the second electrode, and which is opposite to the back electroluminescence portion, And a second bypass portion containing two conductive type impurities.

Here, when the first bypass portion is further included, the first bypass portion may be formed in a plurality of portions, which are partially separated from each other, in a region where the emitter portion and the first electrode overlap each other.

For example, the first electrode may include a plurality of first finger electrodes disposed in a first direction and a plurality of first busbars to which a plurality of first finger electrodes are connected in common. The first bypass unit includes a plurality of first fingers, Electrode or at least one of the plurality of first bus bars.

At this time, the first bypass portion may be electrically connected to the semiconductor substrate through the emitter portion or may be in direct contact with the semiconductor substrate.

In one example, the first bypass portion is covered by the emitter portion and may be in direct physical contact with the emitter portion. In such a case, the first bypass portion may be smaller than the thickness of the emitter portion.

In addition, when the second bypass unit is further included, the second bypass unit may be formed in a plurality of spaces partially separated from each other in a region where the rear electric unit and the second electrode overlap with each other.

For example, when the second electrode includes a second electrode layer disposed entirely on the opposite surface of the semiconductor substrate and a second bus bar electrically connected to the second electrode layer, the second bypass portion may include a plurality of second electrode layers or a plurality of 2 < / RTI > bus bars.

In another example, the second electrode includes a plurality of second finger electrodes disposed in a first direction and a plurality of second bus bars commonly connected to the plurality of second finger electrodes, and the second bypass unit includes a plurality of second finger electrodes, A finger electrode, or a plurality of second bus bars.

At this time, the second bypass portion may be electrically connected to the semiconductor substrate through the rear surface electric portion or may be in direct contact with the semiconductor substrate.

In one example, the second bypass portion is covered by the backside electrical portion and may be in direct physical contact with the backside electrical portion. In such a case, the thickness of the second bypass portion may be smaller than the thickness of the rear electric field portion.

The photovoltaic cell according to the present invention includes a bypass portion in the emitter portion or the backside power portion, so that when the photovoltaic cell is not normally operated due to shadows, a bypass current can flow through the photovoltaic cell.

1 to 6 are views for explaining a solar cell according to a first embodiment of the present invention.
7 to 9 are views for explaining the operation of the solar cell according to the first embodiment of the present invention.
FIGS. 10 to 13 illustrate a solar cell according to a second embodiment of the present invention.
FIGS. 14 to 16 are views for explaining the operation of the solar cell according to the second embodiment of the present invention.
17 is a diagram for explaining a modification of the second embodiment of the present invention.
18 and 19 are diagrams for explaining the difference between the first and second bypass units BP1 and BP2 provided in the solar cell according to the present invention and the bypass diode provided in the junction box JB in general .

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. Further, when a certain portion is formed as "whole" on another portion, it means not only that it is formed on the entire surface of the other portion but also that it is not formed on the edge portion.

Hereinafter, the front surface may be one surface of the semiconductor substrate to which the direct light is incident, and the rear surface may be the opposite surface of the semiconductor substrate in which direct light is not incident, or reflected light other than direct light may be incident.

1 to 6 are views for explaining a solar cell according to a first embodiment of the present invention.

2 is a plan view of the first bypass unit BP1 shown in FIG. 1; FIG. 2 is a plan view of the first bypass unit BP1 shown in FIG. 1; FIG. 5 is a view for explaining another example of the portion K in FIG. 2, and FIG. 6 is a cross-sectional view taken along the line B-B in FIG. And a method of forming the pass section BP1.

1, the solar cell according to the first embodiment of the present invention includes a semiconductor substrate 110, an emitter section 120, a first electrode 140, an antireflection film 130, a rear electric section 172 a back surface field (BSF), and a second electrode 150.

Here, although the rear electric section 172 may be omitted, since the efficiency of the solar cell is further improved when the rear electric section 172 is provided, the following description will be made with reference to an example in which the rear electric section 172 is included.

The semiconductor substrate 110 may be formed of at least one of monocrystalline silicon, polycrystalline silicon, and amorphous silicon containing an impurity of the first conductivity type. In one example, the semiconductor substrate 110 may be formed of a crystalline silicon wafer.

Here, the first conductivity type may be any one of n-type and p-type conductivity types.

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

In the first embodiment of the present invention, the case where the first conductivity type of the semiconductor substrate 110 is n-type will be described as an example.

The semiconductor substrate 110 may have a plurality of uneven surfaces on the entire surface thereof. Accordingly, the emitter section 120 located on the front surface of the semiconductor substrate 110 may also have an uneven surface.

Accordingly, the amount of light reflected from the front surface of the semiconductor substrate 110 decreases, and the amount of light incident into the semiconductor substrate 110 increases.

As shown in FIG. 1, the emitter layer 120 may be formed on one surface of the semiconductor substrate 110, for example, on the front surface. However, this is not essential and may be formed on the back surface of the semiconductor substrate 110.

In addition, the emitter section 120 may include a doped region of a second conductivity type, for example, a p-type conductivity type opposite to the first conductivity type, doped in the semiconductor substrate 110, Lt; / RTI > Thus, the emitter layer 120 of the second conductivity type forms a p-n junction with the semiconductor substrate 110.

Light incident on the semiconductor substrate 110 is separated into electrons and holes, so that the electrons move toward the n-type and the holes move toward the p-type. Therefore, when the semiconductor substrate 110 is n-type and the emitter section 120 is p-type, the separated electrons move toward the back surface of the semiconductor substrate 110 and the separated holes can move toward the emitter section 120.

Since the emitter section 120 forms a pn junction with the first conductive section of the semiconductor substrate 110, that is, the first conductive section of the semiconductor substrate 110, unlike the present embodiment, the semiconductor substrate 110 has a p- The emitter section 120 may have an n-type conductivity type.

When the emitter section 120 has an n-type conductivity type, the emitter section 120 may be formed by doping an impurity of a pentavalent element into the semiconductor substrate 110. Conversely, when the emitter section 120 has a p-type conductivity type, And may be formed by doping an impurity of a trivalent element into the semiconductor substrate 110.

The antireflection film 130 is disposed on the incident surface of the semiconductor substrate 110. When the emitter layer 120 is located on the incident surface of the semiconductor substrate 110 as shown in FIG. 130 may be located above the emitter section 120.

The antireflection film 130 may have a defect such as a dangling bond mainly present on the surface and the vicinity of the semiconductor substrate 110 due to the hydrogen H contained in the antireflection film 130. [ A passivation function may be performed to reduce the loss of charges moving toward the surface of the semiconductor substrate 110 due to defects.

When the semiconductor substrate 110 has the irregular surface, the antireflection film 130 has the irregular surface having a plurality of irregularities similar to the semiconductor substrate 110.

Since the defects are mainly present on or near the surface of the semiconductor substrate 110 in general, the passivation function is further improved if the antireflection film 130 is in direct contact with the surface of the semiconductor substrate 110 as in the case of the embodiment.

The antireflection film 130 may be formed of a hydrogenated silicon nitride film (SiNx: H), a hydrogenated silicon oxide film (SiOx: H), a hydrogenated silicon nitride oxide film (SiNxOy: H), a hydrogenated silicon oxynitride film : H), and hydrogenated amorphous silicon (a-Si: H) may be formed as a single layer or a plurality of layers.

The first electrode 140 may be disposed on the front surface of the semiconductor substrate 110 as shown in FIGS. 1 and 2. The first electrode 140 may be connected to the emitter section 120 through the anti-reflection layer 130.

The first electrode 140 may include a plurality of first finger electrodes 141 and a plurality of first bus bars 142.

The plurality of first finger electrodes 141 may be elongated in the first direction x and the plurality of first bus bars 142 may extend in the first direction x, And may be formed long in the direction y.

In addition, a plurality of first finger electrodes 141 may be electrically connected to the first bus bars 142 at positions intersecting the first bus bars 142.

Here, an interconnector for electrically connecting a plurality of solar cells to each other may be connected to the front surface of the first bus bar 142.

Accordingly, the plurality of first electrodes 140 may be formed of at least one conductive material, such as silver (Ag), to collect electrons, for example electrons, moving toward the emitter section 120.

However, in the first embodiment according to the present invention, the first bus bar 142 may be omitted, and thus, when the first bus bar 142 is omitted, the interconnector for electrically connecting the solar cells to each other And may be connected to the first finger electrode 141.

The backside electrical conductor 172 may be located on the opposite side of one side of the semiconductor substrate 110. For example, as shown in FIG. 1, the backside electrical section 172 may be located on the backside of the semiconductor substrate 110. However, on the contrary, it may be located on the front surface of the semiconductor substrate 110.

In addition, the rear electric field portion 172 may have a region of the first conductive type, which is the same as the semiconductor substrate 110, doped at a higher concentration than the semiconductor substrate 110, for example, an n + region.

Such a rear electric field portion 172 forms a potential barrier through a difference in impurity concentration from the first conductive region of the semiconductor substrate 110 and thereby causes electron movement toward the rear electric field portion 172, While facilitating hole transfer toward the rear electric field 172.

Accordingly, such a rear electric field 172 reduces the amount of electric charges lost due to the recombination of electrons and holes at the back surface and the vicinity of the semiconductor substrate 110 and accelerates the movement of a desired electric charge (e.g., a hole) The amount of charge transfer to the electrode 150 can be increased.

The second electrode 150 may include a second electrode layer 151 and a plurality of second bus bars 152.

The second electrode layer 151 is in contact with the rear electric field portion 172 located on the rear surface of the semiconductor substrate 110 and the second electrode layer 151 is formed on the rear surface of the semiconductor substrate 110 except for the rear edge of the semiconductor substrate 110 and the portion where the second bus bar 152 is located And may be formed entirely on the rear surface of the semiconductor substrate 110 substantially.

The second electrode layer 151 may contain a conductive material such as aluminum (Al), and the second bus bar 152 may be connected to an interconnector.

The second electrode layer 151 may collect electrons, for example electrons, moving from the rear electric field 172 side.

At this time, since the second electrode layer 151 is in contact with the rear electric field portion 172 which maintains the impurity concentration higher than that of the semiconductor substrate 110, the contact resistance between the rear electric field portion 172 and the second electrode layer 151 is reduced The charge transfer efficiency from the semiconductor substrate 110 to the second electrode layer 151 can be improved.

The plurality of second bus bars 152 may be located on the rear surface of the semiconductor substrate 110 where the second electrode layer 151 is not located and may be connected to the adjacent second electrode layer 151.

The plurality of second bus bars 152 may collect charge transferred from the second electrode layer 151.

The plurality of second bus bars 152 are connected to the interconnectors IC so that the charges collected by the plurality of second bus bars 152 Lt; / RTI >

The plurality of second bus bars 152 may be formed of a material having a better conductivity than the second electrode layer 151 and may be formed of a material such as silver (Ag) Conductive material.

Each of the plurality of second bus bars 152 may be connected to each of the interconnectors (IC).

In the solar cell, the solar cell according to the first embodiment of the present invention may further include a first bypass unit BP1 as shown in FIG.

The first bypass unit BP1 may be located in a part of a region where the emitter unit 120 and the first electrode 140 overlap each other and may be electrically connected to the first electrode 140, ) Of the second conductivity type contained in the first conductive type impurity.

The planar position of the first bypass unit BP1 when viewed from the front surface of the semiconductor substrate 110 will be described in more detail with reference to FIGS. 2 and 3. FIG.

FIGS. 2 and 3 are partial plan views of the semiconductor substrate 110 of the solar cell shown in FIG. 1, with the antireflection film 130 and the first electrode 140 omitted. FIGS. 2 and 3 A141 is a portion where the emitter portion 120 and the first finger electrode 141 are overlapped and connected and A142 is a portion where the emitter portion 120 and the first bus bar 142 are overlapped and connected.

The first bypass unit BP1 may be located in a part of the areas A141 and A142 where the emitter part 120 and the first electrode 140 overlap each other when the semiconductor substrate 110 is viewed from the front, The first bypass unit BP1 may be partially formed in a plurality of spaces.

More specifically, for example, when the first electrode 140 includes a plurality of first finger electrodes 141 and a plurality of first bus bars 142 as described above, the first bypass unit BP1, May be overlapped with at least one of the plurality of first finger electrodes 141 or the plurality of first bus bars 142.

2, the first bypass unit BP1 is formed in a first direction x in a region A141 where the emitter unit 120 and the first finger electrode 141 are overlapped with each other, As shown in FIG. 2, the width WBP1 of the first bypass unit BP1 in the second direction y is one example in which the width WF1 of the first finger electrode 141 is the same. However, .

3, the first bypass portion BP1 is formed in a region A 142 in which the emitter portion 120 and the first bus bar 142 are overlapped with each other in the second direction y They may be spaced apart from each other. 3, the width WBP1 of the first bypass unit BP1 in the first direction x is smaller than the width WB1 of the first bus bar 142. However, Or larger.

In FIGS. 2 and 3, the case where a plurality of first bypass portions BP1 are provided is described as an example, but it is also possible to form only one first bypass portion BP1.

A cross section of the solar cell including the first bypass unit BP1 will now be described with reference to FIG. 4 as follows.

4, the first bypass portion BP1, which is located between the emitter portion 120 and the first electrode 140 and contains an impurity of the first conductivity type, is directly connected to the first electrode 140 And can be electrically connected.

Here, the portion of the first electrode 140 connected to the first bypass portion BP1 may contain the impurity DBP1 of the first conductivity type. This is in accordance with a method of manufacturing the first bypass unit BP1. When the manufacturing method is different, a portion of the first electrode 140 connected to the first bypass unit BP1 is an impurity of the first conductivity type DBP1). ≪ / RTI >

In the first bypass unit BP1, the emitter section 120 is positioned between the first bypass section BP1 and the semiconductor substrate 110, and the emitter section 120 is disposed between the semiconductor substrate 110 As shown in FIG.

4, the first bypass unit BP1 may be covered by the emitter unit 120, and the first bypass unit BP1 may be physically in direct contact with the emitter unit 120 .

As described above, when the first bypass unit BP1 is covered with the emitter unit 120, it is possible to prevent the carriers from being recombined in the vicinity of the first bypass unit BP1 due to the emitter unit 120 .

Here, the thickness TBP1 of the first bypass portion BP1 may be smaller than the thickness T120 of the emitter portion 120. [ However, this is not essential, and the thickness TBP1 of the first bypass portion BP1 may be larger than the thickness T120 of the emitter portion 120. [

Here, as shown in FIG. 5 (a), the emitter section 120 is formed such that the impurity of the second conductivity type and the low concentration emitter section 120L doped with the relatively small amount of the impurity of the second conductivity type are relatively And may include a high concentration emitter portion 120H doped with a large amount.

In this case, as shown in FIG. 5A, the high-concentration emitter section 120H may be formed relatively thick at a portion overlapping with the first finger electrode 141, and the low-concentration emitter section 120L may be formed thicker And may be relatively thin at a portion that does not overlap with the first finger electrode 141. Also in this case, the first bypass unit BP1 may be formed to cover the emitter unit 120 and may be directly connected to the first electrode 140 to be electrically connected.

4 and 5A, the case where the first bypass portion BP1 is covered with the emitter portion 120 has been described as an example. Alternatively, as shown in FIG. 5B, 1 bypass portion BP1 may not be formed to cover the emitter portion 120 but may be in direct contact with the semiconductor substrate 110. [

In this case, a small number of some carriers may be recombined in the vicinity of the first bypass unit BP1, but this may cause the size of the area of the first bypass unit BP1 connected to the semiconductor substrate 110 to be appropriately formed , The effect on the efficiency of the solar cell can be minimized.

The first bypass unit BP1 may be formed during the process of forming the first electrode 140. [ This will be briefly described with reference to FIG. 6 as follows.

In order to form a solar cell having a structure as shown in FIG. 1, in order to form a first electrode 140 on a front surface of a semiconductor substrate 110, a first electrode layer 140 for forming a first electrode 140 The eutectic can be applied to the entire surface of the antireflection film 130.

In this case, for example, as shown in FIGS. 2 and 3, when the first bypass unit BP1 is to be formed in a part of the emitter unit 120, as shown in FIG. 6A, A bypass paste P140 containing a conductive type impurity DBP1 may be used.

2 and 3, a portion where the first bypass portion BP1 is to be formed among the regions A141 and A142 in which the first electrode 140 is to be superimposed on the emitter portion 120, The first conductive type impurity DBP1 is contained in the remaining part of the first conductive type DBP1 containing the impurity DBP1 of the first conductive type, The paste can be applied using a paste.

Thereafter, when the semiconductor substrate 110 is heat-treated, the bypass paste P140 and the first electrode paste penetrate the anti-reflection film 130 and are connected to the emitter section 120, and the bypass paste P140 And the first electrode paste may be formed as the first electrode 140 while being dried and cooled.

6B, impurities DBP1 of the first conductivity type included in the bypass paste P140 are connected to portions of the emitter section 120 which are to be formed with the first bypass section BP1, So that the first bypass portion BP1 as described above can be formed.

At this time, impurities DBP1 of the first conductivity type may remain in the first electrode 140 of the portion where the first bypass portion BP1 is formed, and may be partially included.

However, as shown in FIG. 6, when the first electrode 140 is formed, the first bypass portion BP1 is not formed together. For example, before the first electrode 140 is formed, After the first bypass unit BP1 is formed first by using a separate dopant paste containing the impurity DBP1 of the first electrode 140 and then the first electrode 140 is formed by using the first electrode paste , The impurity DBP1 of the first conductivity type may not remain in the first electrode 140.

As described above, the method of forming the first bypass unit BP1 according to the method shown in FIG. 6 is one example, and the first bypass unit BP1 can be formed by any other method.

Thus, when the first bypass unit BP1 is provided in the solar cell, light is incident on the entire surface of the solar cell, and when the solar cell normally operates, the first bypass unit BP1 does not operate, The first electrode 140 and the second electrode 150 are electrically connected to each other by providing a bypass path in the solar cell by performing a turn-on operation when a shadow is formed on the front surface of the solar cell, It can be made conductive. As a result, the bypass current can flow through the shadowed solar cell.

The operation of the solar cell according to the first embodiment of the present invention having such a structure will now be described with reference to FIGS. 7 to 9. FIG.

FIG. 7 is a cross-sectional view taken along the line C2-C2 in FIG. 1, FIG. 8 is a view showing a carrier moving path when the solar cell normally operates, FIG. 9 is a cross- Is bypassed through the first bypass unit BP1 when the first bypass unit BP1 does not normally operate.

In order to explain the operation of the solar cell according to the first embodiment of the present invention, the case where the impurity of the first conductivity type is n-type and the impurity of the second conductivity type is the p-type is shown as an example in FIG. 7, .

Type semiconductor substrate 110, p-type emitter layer 120, and n + -type emitter layer 120. In the case where the impurity of the first conductivity type is n type and the impurity of the second conductivity type is p type, -type, and the first bypass unit BP1 located in the emitter 120 may be n-type.

A plurality of solar cells having such a structure are connected in series to form a module. In each of the first and second electrodes 140 and 150 of the solar cell, interconnectors IC1 and IC2 are connected to electrodes having different polarities of the adjacent solar cells, Lt; / RTI >

7, the first interconnection IC1 connected to the second electrode 150 of another adjacent solar cell may be connected to the first electrode 140 of the solar cell, A second interconnection IC2 connected to the first electrode 140 of another adjacent solar cell may be connected to the second electrode 150 of the second solar cell 150. [

Thus, in the state where the solar cell is connected in series, the solar cell can be operated.

8, when a solar cell is irradiated with light and is incident on the semiconductor substrate 110, electrons (-) and positive (+) pairs are generated in the semiconductor substrate 110 by light energy Lt; / RTI >

The positive (+) electrons move toward the emitter section 120 having the p-type conductivity type and the electrons (-) move toward the rear electric section 172 having the n-type electroconductive type, 140 and the second electrode 150 and may be collected by the first and second electrodes 140 and 150.

Therefore, holes (+) are collected in the first electrode 140 and electrons (-) are collected in the second electrode 150.

The positive electrode (+) that has moved to the first electrode (140) is coupled to the negative (-) electrode that is moved through the first inter connecter (IC1) The current path can be formed by being coupled with the positive (+) electrode that has been moved through the second interconnection IC2.

As a result, a current flows to a plurality of solar cells connected in series to each other, and this can be used as electric power from the outside.

In addition, when the solar cell is not normally operated due to the shadow formed on the entire surface of the solar cell, electrons (-) and holes (+) are not generated in the semiconductor substrate 110 as shown in FIG.

Accordingly, the electrons (-) generated by the other solar cells adjacent to the first electrode 140 can be collected and transferred to the second electrode 150, and the holes (+ Can be moved and collected.

Accordingly, a reverse bias voltage Vrb is applied between the first and second electrodes 140 and 150 of the solar cell, and the p-type emitter portion 120, the n-type semiconductor substrate 110, the n + type A current path can not be formed in the path leading to the backside electric potential 172 of the light emitting diode.

At this time, the magnitude of the reverse bias voltage Vrb is, for example, equal to the magnitude of the open-circuit voltage (Voc) of a typical solar cell, and may take 5 V, which is opposite in voltage direction.

When the reverse bias voltage Vrb applied between the first and second electrodes 140 and 150 of the solar cell increases by a predetermined level (approximately 5 V) or more, the n-type first bypass unit BP1 is turned on The electrons collected by the first electrode 140 pass through the n-type first bypass unit BP1, the p-type emitter unit 120, the n-type semiconductor substrate 110, (+) of the second electrode 150 is moved to the second electrode 150 through a path leading to the n + -type rear electric field 172, A bypass path is formed, and thus a current can flow into the solar cell.

Here, a forward bias voltage is applied between the n-type first bypass unit BP1 and the p-type emitter unit 120 due to the electrons collected by the first electrode 140, Electrons collected by the electrode 140 can move from the n-type first bypass unit BP1 to the p-type emitter unit 120. [

The p-type emitter section 120 overlapped with the first bypass section BP1 has a relatively thin thickness. The p-type emitter section 120 overlaps the first bypass section BP1. Since the band-off voltage between the n-type semiconductor substrates 110 is formed to be smaller than the reverse bias voltage Vrb, the reverse bias voltage Vrb between the first and second electrodes 140 and 150 of the solar cell, electrons (-) transferred to the p-type emitter section 120 can be transferred from the p-type emitter section 120 to the n-type semiconductor substrate 110.

For example, the band-off voltage between the p-type emitter section 120 and the n-type semiconductor substrate 110 overlapping the first bypass section BP1 may have a voltage lower than 5 V, , Or between 0.7V and 4V.

Electrons migrating to the emitter section 120 of the p-type are naturally supplied to the second electrode (not shown) through the path leading to the n-type semiconductor substrate 110 and the n + -type rear electric section 172 150).

As described above, in the solar cell according to the first embodiment of the present invention, when a shadow is generated in the solar cell, and the solar cell does not operate normally, the bypass path BP1 causes the bypass path The efficiency of the solar cell module can be further increased.

In addition, when the reverse bias voltage Vrb is applied between the first and second electrodes 140 and 150 of the solar cell, the temperature of the portion where the solar cell exists in the solar cell module rises due to the reverse bias voltage Vrb Hot spots may occur. If the first bypass unit BP1 is provided in the solar cell as described above, such hot spots can be prevented.

Although only the case where the emitter section 120 is provided with the first bypass section BP1 has been described as an example in order to provide the bypass path to the solar cell up to now, Thereby providing a bypass path to the solar cell.

FIGS. 10 to 13 illustrate a solar cell according to a second embodiment of the present invention.

11 is a plan view of the second bypass portion BP2 shown in FIG. 1, and FIG. 12 is a plan view of the second bypass portion BP2 shown in FIG. 1 when the semiconductor substrate 110 is viewed from the rear side. FIG. 10 is a partial perspective view of the solar cell according to the second embodiment. Fig. 13 is a cross-sectional view taken along line C3-C3 in Fig. 10. Fig.

In the second embodiment of the present invention, the description of the contents overlapping with those described in the first embodiment will be omitted.

As shown in FIG. 10, the solar cell according to the second embodiment of the present invention may further include a second bypass unit BP2 instead of the first bypass unit BP1 described in the first embodiment.

The second embodiment of the present invention will be described with reference to the case where the second bypass unit BP2 is included in place of the first bypass unit BP1. However, the first bypass unit BP1 and the second bypass unit BP2 BP2 may be provided together.

The second bypass unit BP2 may be formed in a part of the area where the rear electric unit 172 and the second electrode 150 are overlapped with each other and may be electrically connected to the second electrode 150, And may include an impurity of the second conductivity type opposite to the impurity of the first conductivity type contained in the step 172.

The planar position of the second bypass unit BP2 when viewed from the rear side of the semiconductor substrate 110 will be described in more detail with reference to FIGS. 11 and 12. FIG.

11 and 12 are partial plan views of the semiconductor substrate 110 of the solar cell shown in FIG. 10 without the second electrode 150 when viewed from the rear. In FIGS. 11 and 12, A 151 denotes a rear electric part 172 and the second electrode layer 151 are overlapped and connected to each other, and A152 is a portion where the rear electric part 172 and the second bus bar 152 are overlapped and connected.

The second bypass unit BP2 may be located in a part of the areas A121 and A122 where the rear electric unit 172 and the second electrode 150 overlap with each other. May be partially separated from each other and formed in plural numbers.

More specifically, for example, when the second electrode 150 includes the second electrode layer 151 and the second bus bar 152 as described above, the second bypass portion BP2 includes a plurality of second May be overlapped and connected to at least one of the electrode layer 151 or the plurality of second bus bars 152.

11, the second bypass portion BP2 may be formed in a plurality of portions that are partially spaced apart from each other in an area A151 in which the rear electric portion 172 and the second electrode layer 151 are overlapped with each other 12, the rear bus bar 172 and the second bus bar 152 may be partially spaced apart from each other to form a plurality of areas A152 overlapping each other.

In FIGS. 11 and 12, the case where a plurality of second bypass portions BP2 are provided has been described as an example, but it is also possible to form only one second bypass portion BP2.

A cross section of the solar cell including the second bypass unit BP2 as described above is as shown in FIG. 13 below.

13, the second bypass unit BP2 formed in a part of the area where the rear electric unit 172 and the second electrode 150 are overlapped with each other is directly connected to the second electrode 150, .

The second bypass unit BP2 includes a backside electrical portion 172 positioned between the second bypass unit BP2 and the semiconductor substrate 110 and electrically connected to the semiconductor substrate 110 through the backside electrical unit 172, As shown in FIG.

Therefore, the second bypass portion BP2 may be covered by the rear electric portion 172, and the second bypass portion BP2 may physically contact the rear electric portion 172 directly.

When the second bypass section BP2 is covered with the rear electric section 172, the second bypass section BP2 is formed by the rear electric section 172 covering the second bypass section BP2, It is possible to prevent the carrier from being recombined in the vicinity.

Here, the thickness TBP2 of the second bypass portion BP2 may be smaller than the thickness T172 of the rear electric portion 172. However, this is not essential, and the thickness TBP2 of the second bypass portion BP2 may be formed to be larger than the thickness T172 of the rear electric section 172. [

Although the second bypass unit BP2 is covered by the rear electric field unit 172 in the example of FIG. 13, the second bypass unit BP2 may be formed directly on the semiconductor substrate 110 It is also possible to contact.

 The operation of the solar cell according to the second embodiment of the present invention having such a structure will now be described with reference to FIGS. 14 to 16. FIG.

Fig. 14 is a cross-sectional view taken along the line C4-C4 in Fig. 10, Fig. 15 is a view showing a carrier path when the solar cell normally operates, Fig. 16 is a cross- Is bypassed through the second bypass unit BP2 when the second bypass unit BP2 does not normally operate.

In order to explain the operation of the solar cell according to the second embodiment of the present invention, FIG. 14 shows an example in which the impurity of the first conductivity type is n-type and the impurity of the second conductivity type is p-type. However, the opposite case is also acceptable.

Type semiconductor substrate 110, p-type emitter layer 120, and n + -type emitter layer 120. In the case where the impurity of the first conductivity type is n type and the impurity of the second conductivity type is p type, -type, and the second bypass unit BP2 may be n-type.

A first interconnection IC1 connected to a second electrode 150 of another adjacent solar cell may be connected to the first electrode 140 of the solar cell having such a structure, , A second interconnector IC2 connected to the first electrode 140 of another adjacent solar cell may be connected.

Thus, in the state where the solar cell is connected in series, the solar cell can be operated.

When the solar cell operates normally, electrons (-) and holes (+) can be generated in the semiconductor substrate 110 by light incident from the outside, as shown in FIG. 15, Electrons move toward the emitter section 120 having the conductive type of the conductive type and the electrons move toward the rear electric section 172 having the n-type conductive type so that the positive electrode + And electrons (-) can be collected in the second electrode 150.

The positive electrode (+) that has moved to the first electrode (140) is coupled to the negative (-) electrode that is moved through the first inter connecter (IC1) The current path can be formed by being coupled with the positive (+) electrode that has been moved through the second interconnection IC2.

As a result, a current flows to a plurality of solar cells connected in series to each other, and this can be used as electric power from the outside.

Thus, when the solar cell normally operates, the second bypass unit BP2 is in a non-operating state.

However, when shadows are formed on the entire surface of the solar cell and the solar cell does not normally operate, electrons and holes are not generated in the semiconductor substrate 110 as shown in FIG.

Accordingly, the electrons (-) generated by the other solar cells adjacent to the first electrode 140 can be collected and transferred to the second electrode 150, and the holes (+ Can be moved and collected.

Therefore, a reverse bias voltage Vrb is applied between the first and second electrodes 140 and 150 of the solar cell and the p-type emitter section 120, the n-type semiconductor substrate 110, and the n + type A current path can not be formed in the path leading to the rear electric section 172. [

However, when the reverse bias voltage Vrb applied between the first and second electrodes 140 and 150 of the solar cell increases by a certain level or more, the second bypass unit BP2 is turned on, Type semiconductor substrate 110, a p-type emitter section 120, and a p-type second bypass section BP2, an n + -type rear electric section 172, an n-type semiconductor substrate 110, And the electron (-) collected in the second electrode 150 is combined with the electrons (-) collected in the second electrode 150 to form a bypass path. Therefore, current can flow into the solar cell.

Here, a forward bias voltage is applied between the second bypass unit BP2 of the p-type and the rear electric field unit 172 of n + -type due to the positive holes collected by the second electrode 150, (+) Can move from the second bypass portion BP2 to the rear electric field portion 172 and the positive (+) which has moved to the rear electric portion 172 naturally moves to the semiconductor substrate 110, -type emitter portion 120 of the first electrode 140. [0033]

As described above, in the solar cell according to the second embodiment of the present invention, when a shadow is generated in the solar cell and the solar cell does not operate normally, the bypass path BP2 allows the bypass path The efficiency of the solar cell module can be further increased, and hot spots can be prevented.

The solar cell according to the second embodiment has described the case where the second electrode 150 includes the second electrode layer 151 and the second bus bar 152. However, The second bypass portion BP2 may be formed in the same pattern as the first electrode 140, as in the second embodiment.

17 is a perspective view of a solar cell according to a modification of the second embodiment of the present invention.

In FIG. 17, description of the same portions as those described in the first and second embodiments described above will be omitted. The structure of the semiconductor substrate 110, the emitter section 120, the rear electric section 172, and the first electrode 140 may be the same as in the second embodiment.

17, in the solar cell according to the modification of the second embodiment, the second electrode 150 includes a plurality of second finger electrodes 151 'arranged in the first direction (x) and a plurality of second bus bars 152, which are arranged in the first direction (y) and in which a plurality of second finger electrodes 151 'are connected in common.

When the second electrode 150 is provided as described above, the second bypass unit BP2 partially overlaps with at least one of the plurality of second finger electrodes 151 'or the plurality of second bus bars 152 .

In such a case, the planar pattern of the second bypass portion BP2 may be formed in a manner similar to that described above with reference to FIG.

18 and 19 are diagrams for explaining the difference between the first and second bypass units BP1 and BP2 provided in the solar cell according to the present invention and the bypass diode provided in the junction box JB in general .

FIG. 18 is a view for explaining bypass diodes BD1 to BD3 provided in the junction box JB of the solar cell module. FIG. 19 is a view for explaining the bypass diodes BD1 to BD3 of FIG. FIG. 4 is a view for explaining a difference in efficiency of generated voltages with the first and second bypass units BP1 and BP2 provided in the solar cell.

As shown in FIG. 18, one solar cell module may include first, second, and third strings ST1, ST2, and ST3 in which a plurality of solar cells are connected in series. Such a solar cell module may be provided with a junction box JB for collecting electric power generated from the first, second and third strings ST1, ST2 and ST3.

In the junction box JB, first, second and third bypass diodes BD1 to BD3 may be provided between the first, second and third strings ST1, ST2 and ST3, respectively.

In this case, for example, when the first solar cell C1 can not be driven due to the shadow, the first bypass diode BD1 is turned on and the junction box JB is turned on in the second and third strings ST2 and ST3 The generated power can be collected.

However, in such a case, not only the first solar cell C1 but also the entire first string ST1 to which the first solar cell C1 belongs can not receive the electric power. As a result, as shown in Fig. 19, A considerable voltage drop of VD1 corresponding to almost 1/3 of the voltage may occur.

However, when the solar cell having the first bypass portion or the second bypass portion is applied to the solar cell module shown in Fig. 18 as in the present invention, only power generated from the corresponding solar cell is not supplied, Power can be supplied from the remaining solar cells of the string to which the battery belongs so that the voltage drop of the solar cell module only results in a relatively small voltage drop of VD2 corresponding to the open-circuit voltage of the first solar cell C1, The efficiency of the battery module can be greatly increased.

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 (14)

A semiconductor substrate containing an impurity of a first conductivity type;
An emitter portion containing an impurity of a second conductivity type opposite to the first conductivity type and disposed on one surface of the semiconductor substrate;
A rear electric field portion containing impurities of the first conductive type at a high concentration than the semiconductor substrate and disposed on the opposite surface of the semiconductor substrate;
A first electrode electrically connected to the emitter; And
And a second electrode electrically connected to the rear electric field portion,
And a first bypass unit electrically connected to the first electrode, the first bypass unit being located in a portion of the emitter region and the first electrode overlapping each other and containing an impurity of the first conductivity type opposite to the emitter region; Further,
A second bypass portion including an impurity of a second conductivity type, which is located at a portion of a region where the rear electric field portion and the second electrode overlap with each other and is electrically connected to the second electrode, ≪ / RTI > The method according to claim 1,
When the first bypass unit is further included,
Wherein the first bypass portion is formed in a plurality of spaces, the first bypass portions being partially separated from each other in a region where the emitter portion and the first electrode overlap with each other. 3. The method of claim 2,
Wherein the first electrode includes a plurality of first finger electrodes arranged in a first direction and a plurality of first bus bars commonly connected to the plurality of first finger electrodes,
Wherein the first bypass unit overlaps at least one of the plurality of first finger electrodes or the plurality of first bus bars. 3. The method of claim 2,
Wherein the first bypass portion is electrically connected to the semiconductor substrate through the emitter portion or directly contacts the semiconductor substrate. 5. The method of claim 4,
And the first bypass portion is covered with the emitter portion. 5. The method of claim 4,
Wherein the first bypass portion is in direct physical contact with the emitter portion. 5. The method of claim 4,
Wherein the first bypass portion is smaller than the thickness of the emitter portion. The method according to claim 1,
When the second bypass unit is further included,
Wherein the second bypass portion is formed in a plurality of spaces, the second bypass portions being partially spaced apart from each other in a region where the rear electric field portion and the second electrode overlap each other. 9. The method of claim 8,
The second electrode includes a second electrode layer disposed entirely on the opposite surface of the semiconductor substrate and a second bus bar electrically connected to the second electrode layer,
Wherein the second bypass unit overlaps at least one of the plurality of second electrode layers or the plurality of second bus bars. 9. The method of claim 8,
Wherein the second electrode includes a plurality of second finger electrodes arranged in a first direction and a plurality of second bus bars commonly connected to the plurality of second finger electrodes,
Wherein the second bypass portion is formed to partially overlap with at least one of the plurality of second finger electrodes or the plurality of second bus bars. 9. The method of claim 8,
Wherein the second bypass portion is electrically connected to the semiconductor substrate through the rear surface electric portion or directly contacts the semiconductor substrate. 12. The method of claim 11,
And the second bypass portion is covered by the rear electric field portion. 12. The method of claim 11,
And the second bypass portion is in direct physical contact with the rear electric field portion. 12. The method of claim 11,
And the second bypass portion is smaller than the thickness of the rear electric field portion.

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