KR101692429B1 - Solar Cell - Google Patents

Abstract

The present invention relates to a solar cell.
A solar cell according to an example of the present invention includes a substrate of a first conductivity type, the substrate including an incident surface on which light is incident and a rear surface on which light is opposite to the incident surface; At least one emitter portion electrically connected to the backside of the substrate and having a second conductivity type opposite to the first conductivity type; A first electrode electrically connected to at least one emitter; And a second electrode back and electrically connected to the substrate, comprises, emitter layer is the number of the Si-Si bond of the interior of ^{7.48 × 10 22 / cm 3 ~} 9.2 × 10 22 / cm 3 Si (Amorphous Silicon, A-Si) layer.

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, and the generated electron-hole pairs are separated into electrons and holes which are charged by the photovoltaic effect, The electrons move toward the semiconductor portion and the holes move toward the p-type semiconductor portion. The transferred electrons and holes are collected by the different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively, and the electrodes are connected by a wire to obtain electric power.

The present invention optimizes the number of Si-Si bonds in an amorphous silicon (A-Si) layer included in a rear-contact solar cell in which electrodes are in contact with the rear surface of a substrate, The purpose is to provide a solar cell.

A solar cell according to an example of the present invention includes a substrate of a first conductivity type, the substrate including an incident surface on which light is incident and a rear surface on which light is opposite to the incident surface; At least one emitter portion electrically connected to the backside of the substrate and having a second conductivity type opposite to the first conductivity type; A first electrode electrically connected to at least one emitter; And a second electrode back and electrically connected to the substrate, comprises, emitter layer is the number of the Si-Si bond of the interior of ^{7.48 × 10 22 / cm 3 ~} 9.2 × 10 22 / cm 3 Si (Amorphous Silicon, A-Si) layer.

Here, the solar cell is disposed between the back and the second electrode of the substrate, the first system unit back former having a conductivity type; further comprising: a rear electric field portion, the number of Si-Si bond of the interior 7.48 × 10 ²² / cm (A-Si) layer having a thickness of ³ to 9.2 x 10 < ²² > / cm < ³ >.

In addition, the solar cell rear protection unit is arranged between the substrate back side and the emitter layer and a back and the back around the system unit of the substrate, further comprising a rear protection unit, the number of Si-Si bond of the interior 7.48 × 10 ²² / cm (A-Si) layer having a thickness of ³ to 9.2 x 10 < ²² > / cm < ³ >.

The solar cell includes a front protection unit is arranged on the incident surface of the substrate, further comprising a front protection unit if the number of the Si-Si bond of the interior ^{7.48 × 10 22 / cm 3 ~} 9.2 × 10 22 / cm 3 of amorphous Silicon (Amorphous Silicon, A-Si) layer.

Here, the number of Si-H bonds in the amorphous silicon layer can be made lower than the number of Si-Si bonds.

Further, the number of Si-H bonds in the amorphous silicon layer can be made higher than the number of unsaturated bonds (dangling bonds).

Also, the amorphous silicon layer may be formed by depositing in a state where the ratio (H2 / SiH4) of the hydrogen hydride (H2) to the silane gas (SiH4) in the chamber is between 3 and 60.

Further, the width of the emitter portion can be made larger than the width of the rear surface electric field portion.

For example, the ratio of the width of the emitter portion to the width of the rear surface electric portion may be between 1.5 and 2.5.

In addition, the thickness of a part of the rear surface protection part located between the rear surface of the substrate and the rear surface protection part located between the rear surface and the emitter part of the substrate, or the thickness of the part of the rear surface protection part positioned between the rear surface and the rear surface part of the substrate, .

The solar cell according to the present invention has the effect of improving the photoelectric conversion efficiency by controlling the number of Si-Si bonds in the amorphous silicon layer as described above.

1 and 2 are views for explaining an example of a solar cell according to the present invention.
3 is a view for explaining the efficiency of a solar cell according to the number of Si-Si bonds in the amorphous silicon layer.
4 is a view for explaining the number of Si-Si bonds according to the ratio of the hydrogen gas and the silane gas.
5 illustrates a solar cell according to another 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.

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 the present invention will be described in detail with reference to the accompanying drawings.

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

FIG. 1 is a partial perspective view of a solar cell according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of the solar cell shown in FIG.

1 and 2, a solar cell 1 according to an exemplary embodiment of the present invention includes a substrate 110, an incident surface (hereinafter, referred to as a 'front surface') that is a surface of a substrate 110 on which light is incident A reflection preventing portion 130 located on the front protective portion 191 and a surface of the substrate 110 which is opposite to the incident surface without light incident thereto a plurality of emitter sections 121 and a plurality of emitter sections 121 located on the rear protection section 192 and a plurality of emitter sections 121 positioned on the rear surface protection section 192, A plurality of spaced apart back surface fields (BSFs) 172 and a plurality of first electrodes 141 and a plurality of back electromotive sections 172 And a plurality of second electrodes 142 disposed on the second electrodes 142. [

1 and 2, a solar cell 1 according to an embodiment of the present invention includes a front surface protection portion 191 (not shown) in addition to the substrate 110, the emitter portion 121, the first electrode 141 and the second electrode 142, The rear surface protection unit 192 and the rear surface electric power unit 172. The front surface protection unit 191, the reflection prevention unit 130, the rear surface protection unit 192, It is also possible to omit the rear electric section 192 and the rear electric section 172.

The substrate 110 is a semiconductor substrate 110 made of silicon of a first conductivity type, for example, n-type conductivity type. At this time, silicon is crystalline silicon such as single crystal silicon or polycrystalline silicon. Impurities of pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb) are doped to the substrate 110 when the substrate 110 has an n-type conductivity type. Alternatively, however, the substrate 110 may be of the p-type conductivity type and may be made of a semiconductor material other than silicon. When the substrate 110 has a p-type conductivity type, the substrate 110 is doped with an impurity of a trivalent element such as boron (B), gallium (Ga), indium (In)

The substrate 110 is textured to have a textured surface, which is an uneven surface. In FIG. 1, only the edge portions of the substrate 110 are shown as textured surfaces, and the front protective portions 191 and the anti-reflection portions 130, which are positioned thereon, also show only the edge portions thereof as uneven surfaces. However, the entire front surface of the substrate 110 substantially has a textured surface, whereby the front protective portion 191 and the antireflective portion 130 located on the front surface of the substrate 110 also have irregularities.

In addition, the substrate 110 may have a textured surface on the back as well as on the front side. In this case, the rear protective part 192, the emitter part 121, the rear electric part 172, and the first and second electrode parts 150 and 140, which are located on the rear surface of the substrate 110, Respectively.

The front surface protection portion 191 located on the front surface of the substrate 110 may include a layer of intrinsic amorphous silicon (a-Si).

The amorphous silicon layer included in the front surface protection portion 191 may have a number of Si-Si bonds therein of between 7.48 × 10 ²² / cm ³ and 9.2 × 10 ²² / cm ³ .

It is possible to change a defect such as a dangling bond mainly present on the surface of the substrate 110 and a vicinity thereof to a stable bond so as to reduce the disappearance of the charge moving toward the surface of the substrate 110 due to the defect Passivation function to reduce the amount of charge lost at or near the surface of the substrate 110 due to defects.

Since the defects are mainly present on the surface of the substrate 110 or in the vicinity of the substrate 110 in general, the front protection portion 191 is in direct contact with the surface of the substrate 110, The loss increases further.

In this embodiment, the front surface protection portion 191 may have a thickness of about 1 nm to 30 nm.

If the thickness of the front protective portion 191 is about 1 nm or more, the passivation function can be satisfactorily performed because the front protective portion 191 is uniformly coated on the entire surface of the substrate 110. If the front protective portion 191 is about 30 nm or less, The amount of light absorbed into the substrate 110 can be reduced and the amount of light incident into the substrate 110 can be increased.

The rear surface protection portion 192 positioned directly on the rear surface of the substrate 110 performs a passivation function in the same manner as the front surface protection portion 191 so as to reduce the disappearance of charges moved toward the rear surface of the substrate 110 due to defects .

Like the front surface protection unit 191, the rear surface protection unit 192 may be formed of amorphous silicon or the like.

The rear shield 192 is thick enough to allow the charge transferred to the backside of the substrate 110 to pass through the rear shield 192 to the plurality of backside electrical parts 172 or the plurality of emitter parts 121 . In this embodiment, one example of the thickness of the rear surface protection 192 may be about 1 to 10 nm.

When the thickness of the rear protective portion 192 is about 1 nm or more, the passivation effect is more uniform because the rear protective portion 192 is uniformly applied to the rear surface of the substrate 110. When the thickness is about 10 nm or less, The amount of light absorbed in the rear surface protection portion 192 is reduced and the amount of light re-incident into the substrate 110 can be increased.

The plurality of rear electric fields 172 are regions in which impurities of the same conductivity type as that of the substrate 110 are doped at a higher concentration than the substrate 110. For example, the plurality of backside electrical sections 172 may be n + impurity regions.

The plurality of rear electric sections 172 are spaced apart from each other on the rear protective portion 192 and extend in a predetermined direction. In this embodiment, the plurality of rear electric sections 172 are made of an amorphous semiconductor such as amorphous silicon (a-Si).

This rear electric field 172 prevents the hole movement toward the rear electric field 172, which is the direction of movement of the electrons, due to the potential barrier due to the difference in impurity concentration between the substrate 110 and the rear electric field 172, (E. G., Electrons) to the electrical system 172. The < / RTI > Accordingly, it is possible to reduce the amount of charge lost due to recombination of electrons and holes at the rear electric field 172 and the vicinity thereof or at the first and second electrode portions 150 and 140, Thereby increasing the amount of electron movement toward the substrate.

Each backside electrical conductor 172 may have a thickness of about 10 nm to 25 nm. If the thickness of the rear electric field 172 is about 10 nm or more, the electric potential barrier that prevents the movement of the holes can be formed more favorably, thereby further reducing the charge loss. If the thickness is about 25 nm or less, The amount of light absorbed can be reduced and the amount of light re-incident into the substrate 110 can be increased.

A plurality of emitter portions 121 are spaced apart from the plurality of rear electrical portions 172 on the rear surface of the substrate 110 and extend parallel to the plurality of rear electrical portions 172.

As shown in FIGS. 1 and 2, the backside electrical portion 172 and the emitter portion 121 are alternately located above the substrate 110.

Each emitter section 121 has a second conductivity type, for example, a p-type conductivity type opposite to the conductivity type of the substrate 110, and is formed of a semiconductor different from the substrate 110, for example, amorphous silicon consist of. Thus, the emitter portion 121 forms a hetero junction as well as a p-n junction with the substrate 110.

Hole pairs that are charges generated by the light incident on the substrate 110 due to the built-in potential difference due to the pn junction formed between the substrate 110 and the plurality of emitter portions 121, And electrons move to the n-type and the holes move to the p-type. Therefore, when the substrate 110 is n-type and the plurality of emitter portions 121 are p-type, the separated holes move through the rear protective portion 192 toward the respective emitter portions 121, And moves to a plurality of rear electric field sections 172 having a higher impurity concentration than the substrate 110. [

Each emitter section 121 forms a pn junction with the substrate 110. Thus, unlike the present embodiment, when the substrate 110 has a p-type conductivity type, the emitter section 121 is an n-type conductivity type I have. In this case, the separated electrons move to the plurality of emitter portions 121 through the rear protective portion 192, and the separated holes move to the plurality of rear electric parts 172 through the rear protecting portion 192.

When the plurality of emitter sections 121 have a p-type conductivity type, the emitter section 121 can be doped with an impurity of a trivalent element. Conversely, when the plurality of emitter sections 121 have an n-type conductivity type , The emitter portion 121 may be doped with an impurity of a pentavalent element.

The plurality of emitter sections 121 can perform a passivation function together with the rear surface protection section 192. In this case, the amount of charge that is extinguished at the rear surface of the substrate 110 due to the defect is reduced, Thereby improving the efficiency.

Each emitter section 121 may have a thickness of about 5 nm to 15 nm. When the thickness of the emitter section 121 is about 5 nm or more, the pn junction can be formed more satisfactorily. When the thickness of the emitter section 121 is about 15 nm or less, the amount of light absorbed in the emitter section 121 is reduced, The amount of light can be increased.

In the present embodiment, due to the rear protective portion 192 of the intrinsic semiconductor material (intrinsic a-Si) located below the plurality of emitter portions 121 and the plurality of rear electric sections 172 and having no or little impurities, When a plurality of emitter portions 121 and a plurality of rear electric fields 172 are formed on a substrate 110 made of a crystalline semiconductor material rather than a plurality of emitter portions 121 and a plurality of rear electric fields 172, The crystallization phenomenon is reduced. As a result, the characteristics of the plurality of emitter portions 121 and the plurality of rear electric sections 172 located on the amorphous silicon are improved.

The plurality of first electrodes 141 located on the plurality of emitter sections 121 extend along the plurality of emitter sections 121 and are electrically connected to the plurality of emitter sections 121. [

The plurality of first electrodes 141 located on the plurality of emitter sections 121 extend long along the plurality of emitter sections 121 and are electrically and physically connected to the plurality of emitter sections 121.

Each first electrode 141 collects charges, for example, holes, which have migrated toward the corresponding emitter section 121.

A plurality of second electrodes 142 located on the plurality of rear electric fields 172 extend along the plurality of rear electric fields 172 and are electrically and physically connected to the plurality of rear electric fields 172 have.

Each second electrode 142 collects a charge, e. G., Electrons, that travels toward the corresponding rear electric field 172.

1 and 2, each of the first and second electrodes 141 and 142 has a planar shape different from that of the emitter portion 121 and the rear electric portion 172 located below the first and second electrodes 141 and 142, . As the contact area between the emitter part 121 and the rear electric part 172 and the first and second electrodes 141 and 142 increases, the contact resistance decreases and the charge transfer efficiency to the electrodes 141 and 142 increases .

The plurality of first and second electrodes 141 and 142 may be formed of at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials. Since the plurality of first and second electrodes 141 and 142 are made of a metal material, the light passing through the substrate 110 is reflected toward the substrate 110.

The solar cell 1 according to the present embodiment having such a structure has a structure in which a plurality of first electrodes 141 and a plurality of second electrodes 142 are positioned on the rear surface of a substrate 110 to which no light is incident, 110 and a plurality of emitter portions 121 are made of different kinds of semiconductors. The operation of the solar cell is as follows.

When the solar cell 1 is irradiated with light and sequentially passes through the antireflection portion 130 and the front surface protective portion 191 and enters the substrate 110, electron-hole pairs are generated in the 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 the 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, and the holes move toward the emitter section 121 having the p-type conductivity type, and electrons move to the n- And are transferred to the first electrode 141 and the second electrode 142, respectively, and are collected by the first and second electrodes 141 and 142, respectively. When the first electrode 141 and the second electrode 142 are connected to each other by a conductor, a current flows and the external power is utilized.

At this time, since the protective portions 192 and 191 are located on the front surface of the substrate 110 as well as the rear surface of the substrate 110, the amount of charge loss due to defects existing on the front surface and the rear surface of the substrate 110 and in the vicinity thereof is reduced The efficiency of the solar cell 1 is improved. At this time, as well as the rear surface protection part 192, the front surface protection part 191 directly contacts the surface of the substrate 110 where the frequency of defects is high, and thus the fading effect is further improved.

At least one of the emitter section 121, the rear electric section 172, and the front surface protection section 191 may include an amorphous silicon layer. The amorphous silicon layer may include a number of Si- Can be formed between 7.48 × 10 ²² / cm ³ and 9.2 × 10 ²² / cm ³ .

This is due to the crystal structure of the amorphous silicon layer. Specifically, amorphous silicon includes three types of intermolecular bonds such as Si-Si bonds, Si-H bonds, and Si-dangling bonds.

Such amorphous silicon does not have a regular crystal structure unlike crystalline silicon having a stable crystal structure of cubic system.

Therefore, the crystal structure of amorphous silicon is unstable, unlike the crystalline structure of crystalline silicon, and the frequency of silicon atoms is relatively higher than that of crystalline silicon, which is dangling bond due to insufficient silicon atom bonding.

Such dangling bonds interfere with the flow of charges when charges flow into the amorphous silicon layer, adversely affecting the efficiency of the solar cell.

However, if the number of Si-Si bonds in the amorphous silicon layer is 7.48 x 10 ²² / cm ³ or more as described above, the dangling bond that can be formed in the amorphous silicon layer can be minimized It is effective.

H bonds in the amorphous silicon layer so that the number of Si-Si bonds in the amorphous silicon layer is 9.2 x 10 < ²² > / cm < ³ > or less. The hydrogen (H) functions not only to increase the bonding force of the amorphous silicon layer but also to improve the mobility of the charge by making the charge flow in the amorphous silicon layer smooth by removing the Si-dangling bonds formed in the amorphous silicon layer . Accordingly, the efficiency of the solar cell can be improved.

This will be described in more detail below.

3 is a view for explaining the efficiency of a solar cell according to the number of Si-Si bonds in the amorphous silicon layer.

FIG. 3 shows data on the relationship between the number of Si-Si bonds in the amorphous silicon layer and the efficiency.

As described above, in order to improve the efficiency of the solar cell including the amorphous silicon layer, the number of Si-Si bonds in the amorphous silicon layer is 7.48 × 10 ²² / cm ³ to 9.2 × 10 ²² / cm ³ .

As shown in FIG. 3, when the number of Si-Si bonds in the amorphous silicon layer is about 7.48 × 10 ²² / cm ³ to 9.2 × 10 ²² / cm ³ , the efficiency is relatively high, about 18.8% to 21.8% .

Considering this, adjusting the number of Si-Si bonds in the amorphous silicon layer to be 7.48 × 10 ²² / cm ³ to 9.2 × 10 ²² / cm ³ is preferable for improving the efficiency of the solar cell including the amorphous silicon layer Can be seen.

On the other hand, when the number of Si-Si bonds in the amorphous silicon layer is about 7.48 × 10 ²² / cm ³ or less, or about 9.2 × 10 ²² / cm ³ or more, the efficiency is as low as about 16% or less.

When the number of Si-Si bonds in the amorphous silicon layer is less than about 7.48 × 10 ²² 2 / cm ³ , the number of Si-Si bonds in the amorphous silicon layer is excessively small, A large number of Si particles are present. Thus, among Si grains, Si grains which do not form Si-Si bond form Si-Dangling bond or Si-H bond. Such Si-Dangling bond or Si-H bond is excessively large in the amorphous silicon layer In this case, the efficiency of the solar cell can be significantly lowered because it can act as a defect.

Further, when the number of Si-Si bonds in the amorphous silicon layer is about 9.2 x 10 ²² / cm ³ or more, the number of Si-Si bonds in the amorphous silicon layer is excessively large, H) particles may be excessively small.

Hydrogen (H) in the amorphous silicon layer is one of the parameters for determining the efficiency of the solar cell. If the amount of hydrogen (H) is excessively small, the amorphous silicon layer itself may have low bonding force and the efficiency of the solar cell may be lowered.

Therefore, considering the efficiency of the solar cell, it is not preferable that the amount of hydrogen is excessively small in the amorphous silicon layer, and the number of Si-Si bonds should be sufficiently large. In addition, it is advantageous that the number of unsaturated bonds (dangling bonds) in the amorphous silicon layer is small.

In addition, hydrogen inside the amorphous silicon layer can form Si-H bonds by bonding with Si grains. Also, within the amorphous silicon layer, the unsaturated bonds can form Si-dangling bonds by bonding with Si grains.

Therefore, considering the efficiency of the solar cell, it is preferable that the number of Si-H bonds in the amorphous silicon layer is lower than the number of Si-Si bonds, and the number of Si-H bonds is higher than the density of unsaturated bonds (dangling bonds) May be preferred.

Next, a method of manufacturing a solar cell according to the present invention will be described with reference to FIG.

4 is a view for explaining the number of Si-Si bonds according to the ratio of the hydrogen gas and the silane gas.

In the solar cell according to the present invention, the amorphous silicon layer can be produced by using a plasma chemical vapor deposition (PECVD) method, wherein hydrogen gas and silane (SiH4) gas can be used as a source gas.

In addition, the number of Si-Si bonds contained in the amorphous silicon layer can be controlled by controlling the ratio of the hydrogen (H2) gas and the silane (SiH4) gas used as the source gas in the chamber of the plasma enhanced chemical vapor deposition .

4, the number of Si-Si bonds in the amorphous silicon layer deposited when the ratio of hydrogen (H2) gas to silane (SiH4) gas (H2 / SiH4) is approximately 100 to 60 is approximately 5.2 x 10 ²² / cm ³ to 7.4 10 ²² / cm ³ .

In this case, as shown in FIG. 3, the number of Si-Si bonds in the amorphous silicon layer is excessively low and the efficiency is low.

It can also be seen that the number of Si-Si bonds in the amorphous silicon layer deposited when the ratio of hydrogen (H2) gas to silane (SiH4) gas (H2 / SiH4) is approximately 2 is approximately 9.7 x 10 ²² / cm ³ .

This case is a case where the number of Si-Si bonds in the amorphous silicon layer is excessively high and the efficiency is low.

On the other hand, hydrogen (H2) gas and silane (SiH4) ratio (H2 / SiH4) in this case is approximately 3 ~ 60 Si-Si bond number inside the amorphous silicon layer is deposited is approximately 7.4 × 10 ²² / cm ³ ~ of the gas 9.18 x 10 < ²² > / cm < ³ >.

In this case, it can be seen from FIG. 3 that the efficiency of the solar cell is high.

Considering this, the amorphous silicon layer can be deposited in an atmosphere having a hydrogen gas (H2) to silane gas (SiH4) ratio of 3: 1 to 60: 1 in the process of manufacturing the amorphous silicon layer.

The PECVD method using hydrogen gas (H2) and silane gas (SiH4) as the source gas has been described as an example. However, any method that forms the amorphous silicon layer using the hydrogen gas (H2) and the silane gas (SiH4) Method can be applied. For example, Photo-CVD, hot-wire CVD, and the like may be applied.

1 to 4, the thickness of the rear surface protection portion 192 is constant and the width of the emitter portion 121 is equal to the width of the rear surface electric portion. However, in order to further improve the efficiency of the solar cell, The thickness of the rear protective portion 192 may be relatively thinner than that of the remaining portion and the width of the emitter portion 121 may be formed to be wider than the width of the rear electric portion 172.

5 illustrates a solar cell according to another embodiment of the present invention.

5, in order to further improve the efficiency of the solar cell, the solar cell according to another example has a structure in which a part of the thickness t2 of the rear surface protection part 192 is relatively thinner than the remaining part, May be formed to be wider than the width of the rear electric section 172. [

5, the remaining portion of the solar cell except for the thickness of the rear surface protection portion 192 and the width of the emitter portion 121 is substantially the same as that of the solar cell shown in FIG. The detailed description thereof will be omitted. 5, at least one of the rear electric section 172 and the front protective section 191 may include an amorphous silicon layer, and the like. The amorphous silicon layer can be formed with a number of Si-Si bonds therein of between 7.48 × 10 ²² / cm ³ and 9.2 × 10 ²² / cm ³ .

5, in another solar cell of the present invention, the width W1 of the emitter section 121 may be greater than the width W2 of the rear electric section 172. As shown in FIG.

The width W1 of the first electrode 141 formed on the emitter section 121 may be greater than the width W2 of the second electrode 142 formed on the rear electric section 172. [

1 and 2, when the substrate 110 is a semiconductor substrate 110 made of n-type conductive silicon, the holes move toward the emitter 121 and electrons move toward the emitter 121, . At this time, by making the width W1 of the emitter section 121 larger than the width of the rear electric section 172, it is possible to shorten the movement distance of the hole, which is the minority carrier, collected by the first electrode 141, Can be further improved.

For example, the ratio W1 / W2 of the width W1 of the emitter section 121 to the width W2 of the rear electric section 172 may be between 1.5 and 2.5.

Here, in order to make the ratio 1: 1.5 or more, the moving distance of the holes is minimized in consideration of the moving speed of electrons and holes, and the ratio is set to 1: 2.5 or less, When the width W1 of the emitter section 121 is excessively large, the width W2 of the rear electric section 172 can be excessively small, So as to secure the width W2 of the electric field portion 172. Thus, the photoelectric efficiency of the solar cell can be optimized.

In addition, the solar cell according to another exemplary embodiment of the present invention may have a structure in which the thickness of a part of the rear surface protection part 192 located between the rear surface of the substrate 110 and the emitter part 121 of the rear surface protection part 192, The thickness t2 of a portion of the rear surface protection part 192 located between the rear surface of the rear surface protection part 192 and the rear surface electric part 172 may be smaller than the thickness t1 of the rest of the rear surface protection part 192. [

Since the rear surface protection portion 192 is formed as described above, electric charges are generated in the rear surface protection portion 192 between the rear surface of the substrate 110 and the emitter portion 121 by the rear electric portion 172 or the emitter portion 121, So that the passivation effect can be further strengthened in the remaining portion of the rear surface protection portion 192. [0051] As shown in FIG.

In the solar cell according to the present invention, the first electrode 141 and the second electrode 142 are connected to the rear surface of the substrate 110. In the rear solar cell, the front surface protection unit 191, (Si-Si bond) of the amorphous silicon layer can be reduced by forming at least one of the emitter layer 192, the emitter layer 121, and the rear electric transistor 172 as an amorphous silicon layer, And the efficiency of the solar cell can be improved by optimizing the thickness of the rear protective portion 192 and the width of the emitter portion 121.

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (10)

A substrate of a first conductivity type including an incident surface through which light is incident and a back surface through which light is opposite the incident surface;
At least one emitter portion electrically connected to a backside of the substrate and having a second conductivity type opposite to the first conductivity type;
A first electrode electrically connected to the at least one emitter section; And
And a second electrode electrically connected to the rear surface of the substrate,
The emitter portion includes an amorphous silicon (A-Si) layer having an inner Si-Si bond number of 7.48 10 ²² / cm ³ to 9.2 10 ²² / cm ³ ,
Wherein the number of Si-H bonds in the amorphous silicon layer is higher than the number of dangling bonds. The method according to claim 1,
The solar cell
And a backside electrical portion disposed between the backside of the substrate and the second electrode, the backside electrical portion having the first conductive type,
Wherein the back electric field portion includes an amorphous silicon (A-Si) layer having an inner Si-Si bond number of 7.48 x 10 ²² / cm ³ to 9.2 x 10 ²² / cm ³ . 3. The method of claim 2,
The solar cell
And a rear protective part disposed between the rear surface of the substrate and the emitter part and between the rear surface of the substrate and the rear electric part,
Wherein the rear surface protection portion comprises an amorphous silicon (A-Si) layer having a number of Si-Si bonds therein of 7.48 10 ²² / cm ³ to 9.2 10 ²² / cm ³ . The method according to claim 1,
The solar cell
And a front protective portion disposed on an incident surface of the substrate,
Wherein the front protective portion comprises an amorphous silicon (A-Si) layer having a number of Si-Si bonds therein of 7.48 10 ²² / cm ³ to 9.2 10 ²² / cm ³ . 5. The method according to any one of claims 1 to 4,
And the number of Si-H bonds in the amorphous silicon layer is lower than the number of Si-Si bonds. delete 5. The method according to any one of claims 1 to 4,
Wherein the amorphous silicon layer is formed by depositing in a state where hydrogen hydrogen (H2) to silane gas (SiH4) ratio (H2 / SiH4) is 3 to 60 in the chamber. 3. The method of claim 2,
And the width of the emitter portion is larger than the width of the rear surface electric field portion. 9. The method of claim 8,
Wherein a ratio of the width of the emitter portion to a width of the rear surface electric portion is between 1.5 and 2.5. The method of claim 3,
Wherein a thickness of a portion of the rear surface protecting portion located between the rear surface of the substrate and the emitter portion or a thickness of a portion of the rear surface protecting portion located between the rear surface of the substrate and the rear surface protecting portion is thinner than a thickness of the remaining portion of the rear surface protecting portion. .

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