KR20130037395A

KR20130037395A - Solar cell

Info

Publication number: KR20130037395A
Application number: KR1020110101778A
Authority: KR
Inventors: 김형석; 고화영; 최정훈
Original assignee: 엘지전자 주식회사
Priority date: 2011-10-06
Filing date: 2011-10-06
Publication date: 2013-04-16

Abstract

PURPOSE: A solar cell is provided to prevent the loss of electric charges by using a first insulating material or a second buffer part which insulates an emitter part and a first electric field part. CONSTITUTION: A substrate(110) has a first conductivity type. A first buffer part(1921) is separated from a second buffer part(1922) on the first surface of the substrate. The first buffer part and the second buffer part are made of amorphous silicon. An emitter part(121) has a second conductivity type which is different from the first conductivity type. A first electric field part(171) is positioned on the second buffer part and has the first conductivity type. A first electrode part(141) is positioned on the emitter part. A second electrode part(142) is positioned on the first electric field 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.

A typical solar cell includes a semiconductor portion for forming a p-n junction by different conductivity types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types, respectively.

When light is incident on the solar cell, a plurality of electron-hole pairs are generated in the semiconductor portion, electrons move toward the n-type semiconductor portion and holes move toward the p-type semiconductor portion by the p-n junction. 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 technical problem to be achieved by the present invention is to improve the efficiency of the solar cell.

Another technical problem to be achieved by the present invention is to increase the design margin of a solar cell.

A solar cell according to an aspect of the present invention is a substrate made of a crystalline semiconductor and having a first conductivity type, a first buffer portion located directly on the first side of the substrate and made of amorphous silicon, directly on the first side of the substrate. A second buffer portion positioned and made of amorphous silicon, positioned on the first buffer portion, and formed of an amorphous semiconductor, and having an emitter portion having a second conductivity type different from the first conductive type, and formed of an amorphous semiconductor positioned on the second buffer portion And a first electric field part having the first conductivity type, a first electrode part directly located on the emitter part, and a second electrode part directly located on the first electric field part, wherein a part of the emitter part and the rear electric field are included. Some of the portions overlap each other, and the first buffer portion or the second buffer portion overlaps with each other. And a first thickness of the first buffer portion or the second buffer portion located between the overlapping emitter portion and the backside electric field portion on the first surface of the substrate. It may be thicker than a second thickness of the first buffer portion or the second buffer portion located.

The first thickness may be 1 nm to 10 nm, and the second thickness may be 10 nm to 200 nm.

The first buffer portion and the second buffer portion may be made of amorphous silicon.

The emitter part and the first electric field part may be separated from each other.

The substrate may have a first portion and a second portion having different thicknesses.

One of the emitter portion and the first electric field portion may be positioned on the first portion, and the other of the emitter portion and the first electric field portion may be positioned on the second portion.

The first portion may have a thickness of 100 μm to 150 μm, and the second portion may have a thickness of 200 μm to 250 μm.

The solar cell according to the above feature may overlap the first buffer portion or the second buffer portion with an intervening layer, and further include an insulating film between the emitter portion and the first electric field portion.

The insulating layer may be positioned directly on one of the emitter unit and the first electric field unit.

The insulating layer may be positioned between the first electric field portion and the first buffer portion overlapping each other, or the emitter portion and the second buffer portion overlapping each other.

The insulating layer may be positioned between the first buffer portion and the emitter portion overlapping each other, or the second buffer portion and the first electric field portion overlapping each other.

The thickness of the first buffer portion or the second buffer portion located between the overlapping emitter portion and the backside electric field portion is equal to the thickness of the first buffer portion or the second buffer portion located on the first surface of the substrate. May be the same.

The insulating layer may have a thickness of about 10 nm to about 200 nm.

The first buffer portion and the first buffer portion are separated from each other, and the insulating film is directly over a portion of the first surface of the substrate exposed between the first buffer portion and the second buffer portion, and the emi It may be further located between the side of the turret portion and the second buffer portion or between the side of the first electric field portion and the first buffer portion.

The solar cell according to the above feature may further include a buffer unit formed of an amorphous semiconductor on a second surface of the substrate positioned opposite to the first surface.

The solar cell according to the above feature may further include a second electric field part formed of an amorphous semiconductor on the second surface of the substrate opposite to the first surface and having the first conductivity type.

According to a feature of the present invention, since the adjacent emitter portion and the first electric field portion are disposed to overlap each other with the first or second buffer portion interposed therebetween, the design margin of the emitter portion or the first electric field portion is increased to facilitate the design of the solar cell. Become.

In addition, since the emitter portion and the first electric field portion are electrically insulated from the first or second buffer portion, which is an insulating material, the amount of charge loss is reduced and the efficiency of the solar cell is improved.

1 is a partial perspective view of an example of a solar cell according to one embodiment of the invention.
FIG. 2 is a cross-sectional view of the solar cell illustrated in FIG. 1 taken along the line II-II.
3 is a cross-sectional view showing a part of another example of a solar cell according to an embodiment of the present invention.
4 and 5 are cross-sectional views each showing a part of another example of a solar cell according to an embodiment of the present invention.
6 and 7 are cross-sectional views each showing a part of an example of a solar cell according to another embodiment of the present invention.
8 and 9 are cross-sectional views each showing a part of another example of a solar cell according to another embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above another portion but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. In addition, when a part is formed "overall" on another part, it means that not only is formed on the entire surface of the other part but also is not formed on a part of the edge.

Next, a solar cell as an embodiment of the present invention will be described with reference to the accompanying drawings.

Referring to FIG. 1, a solar cell 11 according to an exemplary embodiment of the present invention is positioned on an entrance surface (hereinafter, referred to as a “front surface”) that is a surface of a substrate 110 and a substrate 110 to which light is incident. Anti-reflection located on the front buffer region 191, the front surface field (FSF) portion 171 located on the front buffer portion 191, and the front field portion 171 A portion 130, a plurality of emitter regions 121 and a rear surface of the substrate 110 positioned on a surface of the substrate 110 that is opposite to the incident surface (hereinafter, referred to as a “back surface”). A plurality of back surface field (BSF) regions 172 located above and spaced apart from the plurality of emitter portions 121, respectively, a plurality of emitter portions 121 and a plurality of back field fields 172, respectively. A plurality of first and second auxiliary electrodes 151 and 152 and a plurality of first and second main electrodes 141 and 142 respectively positioned on the plurality of first and second auxiliary electrodes 151 and 152.It should.

In this case, the first auxiliary electrode 151 and the first main electrode 141 positioned thereon form a first electrode portion, and the second auxiliary electrode 152 and the second main electrode 142 positioned thereon are formed of a first electrode part. Two electrode portions are formed.

Generally, light is not incident through the rear surface of the substrate 110, but in some cases, light may be incident to the rear surface of the substrate 110. In this case, the amount of light incident through the rear surface of the substrate 110 is much smaller than the amount of light incident through the front surface of the substrate 110.

The substrate 110 is a semiconductor substrate made of silicon of a first conductivity type, for example, an n-type conductivity type. In this case, since silicon is crystalline silicon such as monocrystalline silicon or polycrystalline silicon, the substrate 110 is a crystalline semiconductor substrate.

When the substrate 110 has an n-type conductivity type, impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb), and the like are doped into the substrate 110. Alternatively, the substrate 110 may be of a 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 impurities of trivalent elements such as boron (B), gallium (Ga), indium (In), and the like.

Unlike FIGS. 1 and 2, the front surface of this substrate 110 may have a textured surface that is an uneven surface with an irregular surface through a texturing process. At this time, the texturing process is performed over the entire surface of the substantially flat substrate 110.

In this case, substantially the entire front surface of the substrate 110 has a concave-convex surface, and thus, the front buffer portion 191, the front electric field portion 171, and the anti-reflection portion 130 positioned on the front surface of the substrate 110 also have the same. Has uneven surface

As such, when the entire surface of the substrate 110 is textured, the incident area of the substrate 110 increases and the light reflectivity decreases, thereby increasing the amount of light incident on the substrate 110, thereby increasing the efficiency of the solar cell 11. This is improved.

The front buffer part 191 positioned on the front surface of the substrate 110 is made of an amorphous semiconductor. For example, the front buffer part 191 is made of intrinsic amorphous silicon (i-Si).

In this case, the front buffer unit 191 may be entirely located on the front surface of the substrate 110 or may be located on the front surface of the substrate 110 except for the edge portion of the front surface of the substrate 110.

The front buffer part 191 uses a hydrogen (H) contained in the front buffer part 191 to detect defects such as dangling bonds mainly existing on and near the surface of the substrate 110. The amount of charge lost on and near the surface of the substrate 110 by the defect by performing a passivation function that reduces the dissipation of charge transferred to the surface of the substrate 110 by the defect by switching to a stable bond. Decreases.

In general, since defects are mainly present on or near the surface of the substrate 110, in the case of the embodiment, since the front buffer portion 191 is directly in contact with the surface of the substrate 110, the passivation function is further improved, and the amount of charge loss is increased. Is further reduced.

In the present embodiment, the front buffer part 191 may have a thickness of about 1 nm to 10 nm.

If the thickness of the front buffer part 191 is about 1 nm or more, the front buffer part 191 is uniformly coated on the entire surface of the substrate 110, so that the passivation function may be satisfactorily performed. The amount of light incident in the substrate 110 may be increased by reducing the amount of light absorbed in the 191.

The front field unit 171 positioned on the front buffer unit 191 may be formed of an amorphous semiconductor, for example, amorphous silicon (a-) containing impurities of the same conductivity type (eg, n-type) as the substrate 110. Si), and the concentration of the impurity of the first conductivity type contained in the front buffer portion 191 has a higher concentration than that of the substrate 110. As a result, the front electric field part 171 forms a hetero junction with the substrate 110. When the front electric field part 171 has an n-type conductivity type, impurities of the pentavalent element may be doped into the front electric field part 171.

The front electric field unit 171 forms a potential barrier due to a difference in impurity concentration with the substrate 110 to perform a front electric field function that prevents hole movement toward the front surface of the substrate 110. Accordingly, the front surface field effect is obtained in which holes moving toward the front surface of the substrate 110 by the front surface electric field portion 171 are returned to the rear surface of the substrate 110 by the potential barrier. The output amount of holes output to the external device through the rear surface is increased, and the amount of charge lost by recombination or defects in the front surface of the substrate 110 is reduced.

In addition, an open voltage Voc of the solar cell 11 is increased due to a difference in energy band gap due to heterojunction between the front electric field unit 171 and the substrate 110.

The front electric field unit 171 performs a passivation function together with the front buffer unit 191 as well as the front electric field function. That is, like the front buffer unit 191, the front electric field unit 171 also performs a passivation function using hydrogen (H) contained in the front electric field unit 171. As a result, since the passivation function of the front buffer part 191 having a thin thickness is stably supplemented, the passivation effect is stably obtained at the front surface of the substrate 110.

The anti-reflection unit 130 located on the front electric field unit 171 reduces the reflectivity of light incident on the solar cell 11 and increases the selectivity of a specific wavelength region, thereby increasing the efficiency of the solar cell 11.

The anti-reflection unit 130 is made of a transparent material such as hydrogenated silicon nitride (SiNx: H), hydrogenated amorphous silicon nitride (a-SiNx: H), hydrogenated silicon oxide (SiOx: H), and the like. It may have a thickness of nm to 90nm.

The anti-reflection unit 130 may have a better transmittance of light within this thickness range, thereby further increasing the amount of light incident toward the substrate 110.

In the present exemplary embodiment, the anti-reflection unit 130 may have a single layer structure but may have a multilayered layer structure such as a double layer. The anti-reflection unit 130 also performs a passivation function similar to the passivation function of the front electric field unit 171 and the front buffer unit 191.

Since silicon nitride and silicon oxide have positive fixed charge characteristics, when the antireflection portion 130 is made of these materials, the fixed charge value of the antireflection portion 130 is positive ( +)

As a result, holes acting as minority carriers in the n-type substrate 110 have the same polarity as the anti-reflective unit 130, and thus, the anti-reflective unit 130 is prevented by the polarity of the anti-reflective unit 130. The other side where the is located, that is, the plurality of emitters 121 is output is pushed toward the rear side of the substrate 110 is located.

Therefore, by the anti-reflection portion 130, the amount of holes moving toward the front surface of the substrate 110 is reduced to reduce the amount of holes lost by defects or lost by recombination at the front surface of the substrate 110, In addition, the amount of holes moving toward the rear surface of the substrate 110 in which the plurality of emitters 121 are located increases.

Accordingly, the efficiency of the solar cell 11 is improved by the passivation function of the front buffer part 191 and the anti-reflection part 130 and the fixed charge role of the anti-reflection part 130 positioned on the front surface of the substrate 110. do.

In the present exemplary embodiment, at least one of the front buffer part 191, the front electric field part 171, and the anti-reflection part 130 positioned on the front surface of the substrate 110 may be omitted as necessary.

The rear buffer unit 192 disposed on the rear surface of the substrate 110 includes a plurality of first rear buffer portions 1921 and a plurality of second rear buffer portions 1922.

In this case, the first and second rear buffer portions 1921 and 1922 are alternately positioned on the substrate 110 and extend in parallel to each other in a predetermined direction, and the first and second rear buffer portions 1921 and 1922 are the substrate 110. Just above the rear of the car.

In this example, the first rear buffer portion 1921 partially overlaps on the second rear buffer portion 1922.

Thus, as shown in FIG. 1, the first rear buffer portion 1921 is formed on the rear surface of the substrate 110 where the second rear buffer portion 1922 is not located, and the side surface of the adjacent second rear buffer portion 1922. It is positioned on the side of the rear electric field 172 located above the second rear buffer portion 1922 and above the upper portion of the adjacent rear electric field 172. In this case, the first rear buffer portion 1921 is continuously formed without interruption. Thus, the width W1 of each first rear buffer portion 1921 is greater than the width W2 of each second rear buffer portion 1922, and the horizontal length L1 of each first rear buffer portion 1921. Is greater than the horizontal length L2 of each second backside buffer portion 1922.

In addition, the width W21 of the lower surface of the first rear buffer portion 1921 in contact with the rear surface of the substrate 110 is the width of the lower surface of the second rear buffer portion 1922 in contact with the rear surface of the substrate 110. It may be greater than (W22). Accordingly, the amount of charge transfer to the first rear buffer portion 1921 through which holes having a mobility lower than that of electrons move increases, so that the first auxiliary electrode 151 and the second auxiliary electrode due to the difference in mobility between electrons and holes are increased. The charge collection difference of 152 is compensated for.

Here, the horizontal lengths L1 and L2 are the total length of each of the first and second rear buffer portions 1921 and 1922 extending in a direction crossing the extending directions of the first and second rear buffer portions 1921 and 1922. And the widths W1 and W2 are the widths of each of the first and second backside buffer portions 1921 and 1922 located above the backside of the substrate 110.

In the present embodiment, each of the first rear buffer portion 1921 and the second rear buffer portion 1922 has a different thickness depending on the position.

For example, as illustrated in FIGS. 1 and 2, the thickness T1 of the first rear buffer portion 1921 and the second rear buffer portion 1922 directly contacting the substrate 110 may be the second rear surface. It is thinner than the thickness T2 of the portion of the first backside buffer portion 1921 that overlaps the buffer portion 1922.

The first rear buffer portion 1921 and the second rear buffer portion 1922 may be made of the same material, and the first and second rear buffer portions 1921 and 1922 may be the same as the front buffer portion 191. It may be made of a material. Thus, the first and second backside buffer portions 1921 and 1922 may be made of intrinsic amorphous silicon (i-a-Si).

However, in other examples, the first and second backside buffer portions 1921 and 1922 may be made of a non-conductive material, such as an oxide based or silicon nitride based material. At this time, the hydrogenation process may be performed by a gas supplied to form the rear buffer unit 192, and in this case, the rear buffer unit 192 may contain hydrogen (H). Therefore, in this case, the rear buffer unit 192 may be made of a hydrogenated non-conductive material.

The rear buffer unit 192 performs a passivation function on the rear surface of the substrate 110 similarly to the front buffer unit 191. This reduces the dissipation of charges that have migrated toward the backside of the substrate 110 by unstable coupling.

Part of the first rear buffer portion 1921 of the rear buffer portion 192 which is directly in contact with the substrate 110 and the second rear buffer portion 1922 have charges moved toward the rear surface of the substrate 110. It has a thickness that can move through the second rear buffer portions 1921 and 1922 to the plurality of emitter portions 121 and the rear electric field portion 172. The thickness T1 of the portion of the first backside buffer portion 1921 directly in contact with the substrate 110 and the thickness T1 of each of the second backside buffer portion 1922 are equal to each other, for example, the thickness of these portions. (T1) may be about 1 nm to 10 nm.

For this reason, as described above, the thickness T2 of the remaining portion of the first rear buffer portion 19221 that is not in contact with the substrate 110 and overlaps the second rear buffer portion 1922 is greater than the thickness T1. Since it is thick, it may have a value of about 10 nm or more.

If the thickness T1 of each of the first and second rear buffer portions 1921 and 1922 is about 1 nm or more, the passivation is performed since the first and second rear buffer portions 1921 and 1922 are more uniformly coated on the rear surface of the substrate 110. Function can be better performed, and if the thickness T1 of each of the first and second buffer protection portions 1921 and 1922 is about 10 nm or less, the charge transfer is made easier and the first and second rear buffer portions The amount of light re-incident into the substrate 110 may be further increased by further reducing the amount of light absorbed through the substrate 110 in the 1921 and 1922.

A plurality of emitter portions 121 are positioned over the top surfaces of the plurality of first rear buffer portions 1921, and each emitter portion 121 is each first rear buffer portion over the top surface of each first rear buffer portion 1921. (1921) extends in a predetermined direction.

As shown in FIG. 1, each emitter portion 121 has the same planar shape as the first rear buffer portion 1921 located below.

Each emitter portion 121 is an impurity portion having a second conductivity type that is opposite to the conductivity type of the substrate 110, for example, a p-type conductivity type, and is an amorphous semiconductor that is a semiconductor different from the substrate 110. For example, it consists of amorphous silicon. Thus, each emitter portion 121 forms a heterojunction as well as a p-n junction with the substrate 110.

When the plurality of emitter portions 121 have a p-type conductivity type, the emitter portion 121 may include impurities of trivalent elements, and conversely, the plurality of emitter portions 121 may have n-type conductivity types. In this case, the pentavalent element may contain impurities.

As such, due to the built-in potential difference due to the pn junction formed between the substrate 110 and the plurality of emitter units 121, electrons and holes, which are charges generated by light incident on the substrate 110, They move toward the n-type semiconductor portion and the p-type semiconductor portion, respectively. Therefore, when the substrate 110 is n-type and the plurality of emitter portions 121 are p-type, the holes penetrate through the plurality of first rear buffer portions 1921 of the rear buffer portion 192 and thus the plurality of emitter portions 121. Electrons move through the plurality of second rear buffer portions 1922 of the rear buffer portion 192 to the plurality of rear electric field portions 172 having a higher impurity concentration than the substrate 110.

Since each emitter portion 121 forms a pn junction with the substrate 110, unlike the present embodiment, when the substrate 110 has a p-type conductivity type, the emitter portion 121 has an n-type conductivity type. Have In this case, the electrons move toward the plurality of emitter portions 121 through the plurality of first rear buffer portions 1921 of the rear buffer portion 192, and holes are provided in the plurality of second rear buffer portions of the rear buffer portion 192. It moves toward the plurality of rear electric fields 172 through 1922.

The plurality of rear electric field portions 172 are positioned on an upper surface of the second rear buffer portion 1922 of the rear buffer portion 192, and each of the rear electric field portions 172 is an upper portion of each second rear buffer portion 1922. It extends in a predetermined direction along each second rear buffer portion 1922 over the plane.

As shown in FIG. 1, each backside electric field 172 has the same planar shape as the second backside buffer portion 1922 located below it.

The plurality of rear electric field parts 172 are made of amorphous silicon in the same way as the front electric field parts 171, and impurity parts containing impurities of the same conductivity type as the substrate 110 at a higher concentration than the substrate 110, for example, n + part.

As a result, a potential barrier is formed due to the difference in the impurity concentration between the substrate 110 and the plurality of rear electric field parts 172, similarly to the front electric field part 171, and thus the plurality of second rear buffers of the rear buffer part 192. The amount by which electrons and holes are recombined and extinguished in the vicinity of the plurality of second electrodes 142 is prevented since charges passing through the portion 1922, for example, holes, are prevented from moving toward the plurality of second electrodes 142. This decreases.

In this example, a portion of each first back buffer portion 1921, that is, a portion that overlaps with a second back buffer portion 1922, partially overlaps an adjacent back field 172, so that each first back buffer portion 1921 is located above a portion of the upper surface along the side of the adjacent rear electric field 172.

In this example, the lower surface of the rear electric field 172 is a surface in contact with the second rear buffer portion 1922, and the upper surface of the rear electric field 172 is a surface opposite to the lower surface of the second auxiliary electrode 152. ) Is in contact with the side.

As a result, each first rear buffer portion 1921 is positioned to overlap the second rear buffer portion 1922 with the rear electric field portion 172 disposed therebetween.

As described above, the thickness T2 of the first rear buffer portion 1921 positioned over the rear electric field 172 and overlapping the rear electric field 172 is greater than the thickness T1 of the remaining portions, As described, the thickness T2 of the first rear buffer portion 1921 overlapping the rear electric field 172 may be, for example, about 10 nm to 200 nm.

In addition, as described above, since the emitter portion 121 is positioned on the first rear buffer portion 1921 and has the same planar shape as the first rear buffer portion 1921, each emitter portion 121 is positioned at the lower portion thereof. The first rear buffer portion 1921 partially overlaps the adjacent rear electric field 172.

In this case, the width W3 of the first rear buffer portion 1921 overlapping the rear electric field 172 may be about 5 μm or more and less than 1/2 of the width W2 of each rear electric field 172. . As such, each emitter part 121 and the rear electric field part 172 adjacent to each other are disposed in the vertical direction of the substrate 110, that is, in the vertical direction of the rear surface of the substrate 110 with the first rear buffer part 1921 interposed therebetween. Since they overlap, the emitter portion 121 and the rear electric field portion 172 adjacent to each other remain electrically insulated.

When at least a portion of the emitter portion 121 and the rear electric field portion 172 adjacent to each other are in contact with each other, in the region where the emitter portion 121 and the rear electric field portion 172 are in contact with each other, the second conductivity type (for example, p-type) Impurities and the first conductivity type (e.g., n-type) are mixed with each other, and these p-type impurities and n-type impurities do not contribute to the formation of the emitter portion 121 and the backside electric field portion 172, respectively, and transfer charges. Will interfere with and cause defects. Therefore, when there is a region where the emitter unit 121 and the rear electric field unit 172 are in contact with each other, the electric charges (for example, holes) moved to the emitter unit 121 and the electric charges moved to the rear electric field unit 172 ( For example, a problem arises in that the electrons) are recombined with each other, and a loss amount due to defects caused by doped p-type and n-type impurities is increased.

However, as shown in the present example, since the emitter portion 121 and the rear electric field portion 172 adjacent to each other by the first rear buffer portion 1921 are electrically and physically insulated, the amount of charge lost due to the recombination of electrons and holes. This decreases.

In addition, since the thickness T2 of the first rear buffer portion 1921 positioned between the emitter portion 121 and the rear electric field portion 172 overlapping each other is thicker than the thickness T1 of the other portion, the emitter portion 121 And the insulation effect between the back electric field part 172 is further improved. In this case, the thickness T2 of the first rear buffer portion 1921 positioned between the emitter portion 121 and the rear electric field portion 172 overlapping each other may be defined between the overlapped emitter portion 121 and the rear electric field portion 172. It is a value that can reliably prevent electrical interference.

When the thickness T2 of the first rear buffer part 1921 positioned between the emitter part 121 and the rear electric field part 172 overlapping each other is about 10 nm or more, the emitter part 121 and the rear electric field overlapping each other are overlapped. The electrical interference between the system unit 172 is more stable, and the thickness T2 of the first rear buffer part 1921 positioned between the emitter unit 121 and the rear electric field unit 172 overlapping each other is about 200 nm. In the following case, electrical interference between the emitter part 121 and the rear electric field part 172 superimposed on each other without unnecessary thickness increase and manufacturing time increase is stably maintained.

In addition, when the plurality of emitter portions 121 are designed after the plurality of rear electric field portions 172 are designed, the emitter portions 121 may be designed to overlap with the adjacent rear electric field portions 172. The design margin of the emitter portion 121 increases.

At this time, when the width W3 of the first rear buffer portion 1921 overlapping with the rear electric field 172 is 5 μm or more, the design margin of the emitter unit 121 positioned on the rear electric field 172 is stable. The emitter portion 121 is stably formed on the rear electric field portion 172 and the width W3 of the first rear buffer portion 1921 overlapping the rear electric field portion 172 is increased. When less than 1/2 of the width W2 of 172, the second electrode portion positioned on the rear electric field portion 172 is stably positioned.

In addition, the plurality of emitter portions 121 and the plurality of backside electric fields 172 are not directly positioned on the substrate 110 made of crystalline semiconductor, and are formed of an amorphous semiconductor material such as amorphous silicon, silicon oxide, or silicon nitride. Since the plurality of emitters 121 and the plurality of rear electric field parts 172 are disposed on the rear buffer part 192, the crystallization phenomenon due to the substrate 110, which is a crystalline semiconductor, is not affected. As a result, the heterojunction effect between the emitter unit 121, the rear buffer unit 192, and the substrate 110 is stably maintained, and the efficiency of the solar cell 11 is improved.

As with the rear buffer unit 192, the front buffer unit 191 is also located between the substrate 110 and the front electric field unit 171, so that the front buffer unit 191 has a crystallization phenomenon due to the substrate 110. Blocking affecting the electric field unit 171.

The plurality of first auxiliary electrodes 151 positioned on the plurality of emitter units 121 and the plurality of second auxiliary electrodes 152 positioned on the plurality of rear electric fields 172 are each emitter 121 and each rear electric field unit. It extends along 172 and is made of a transparent conductive material, such as transparent conductive oxide (TCO). Therefore, the plurality of emitters 121 and the plurality of rear electric field parts 172 are electrically connected to each other.

By the first and second auxiliary electrodes 151 and 152, each emitter part 121 and the rear electric field part 172 are protected from oxygen in the air, thereby preventing characteristic changes due to oxidation.

Examples of the transparent conductive material may be ITO, ZnO, SnO ₂ , a compound thereof, or a material doped with a material such as aluminum (Al), germanium (Ge), gallium (Ga), iron (F), or the like. have.

The plurality of first and second auxiliary electrodes 151 and 152 transfer charges, for example, holes and electrons, respectively, which are moved toward the plurality of emitter portions 121 and the plurality of rear electric field portions 172, respectively, The light passing through the 110 is reflected toward the substrate 110 to function as a reflector to increase the amount of light incident on the substrate 110.

However, in an alternative example, the plurality of first and second auxiliary electrodes 151, 152 may be omitted.

The plurality of first main electrodes 141 positioned on the plurality of first auxiliary electrodes 151 extends along the plurality of first auxiliary electrodes 151 and is electrically connected to the plurality of first auxiliary electrodes 151. It is physically connected. 1 and 2, each of the first main electrodes 141 has the same planar shape as the first auxiliary electrode 151 positioned below, but may have a different planar shape.

Each first main electrode 141 moves toward the corresponding emitter part 121 to collect charges, for example, holes, transmitted through the first auxiliary electrode 151. At this time, as described above, since the thickness of the first auxiliary electrode 151 is different depending on the position, the efficiency of charge collection from each emitter portion 121 to the first auxiliary electrode 151 is improved, thereby providing the first primary. The amount of charge output from the electrode 141 increases.

The plurality of second main electrodes 142 positioned on the plurality of second auxiliary electrodes 152 extend along the plurality of second auxiliary electrodes 152 and are electrically connected to the plurality of second auxiliary electrodes 152. It is physically connected. 1 and 2, each second main electrode 142 also has the same planar shape as the second auxiliary electrode 152 disposed below, but may have a different planar shape.

Each second main electrode 142 moves toward the corresponding backside field portion 172 and collects the charge, for example, electrons transferred through the second auxiliary electrode 152.

The first and second main electrodes 141 and 142 may include nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin (Sn), zinc (Zn), indium (In), It may be made of at least one conductive material selected from the group consisting of titanium (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials other than the above.

In this example, the plurality of emitter portions 121, the plurality of backside electric fields 172, and the plurality of first main electrodes 141 and the plurality of second main electrodes made of a semiconductor material such as amorphous silicon A plurality of first auxiliary electrodes 151 and a plurality of second auxiliary electrodes 152 made of a transparent metal material are present between the 142 to improve adhesion between the semiconductor material and the metal material, which have weak adhesion (contact characteristics). As a result, the adhesive force between the plurality of emitter portions 121 and the plurality of first main electrodes 141 and between the plurality of rear electric field portions 172 and the plurality of second main electrodes 142 is improved.

In addition, an ohmic contact is formed between the plurality of emitter parts 121 and the plurality of first main electrodes 141 and between the plurality of rear electric field parts 172 and the plurality of second main electrodes 142, thereby providing a plurality of emits. The electrical conductivity between the turb portion 121 and the plurality of first main electrodes 141 and between the plurality of rear electric field portions 172 and the plurality of second main electrodes 142 is improved, thereby, the first and second The transfer efficiency of charges to the main electrodes 141 and 142 increases.

When the plurality of first and second auxiliary electrodes 151 and 152 are omitted, each of the first electrode 141 and each of the second electrodes 142 may correspond to the corresponding emitter portion 121 and the back electric field portion 172. Directly on the

When the first and second auxiliary electrodes 151 and 152 are omitted, each of the first electrode 141 and each second electrode 142 is disposed on the corresponding emitter portion 121 and the corresponding rear electric field portion 172. Directly located. In this case, the time and manufacturing cost for forming the plurality of first and second auxiliary electrodes 151 and 152 are reduced, thereby reducing the manufacturing cost of the solar cell 11.

In addition, a first electrode part including the first auxiliary electrode 151 and the first electrode 141 is in direct contact with the emitter part 121, and a second electrode including the second auxiliary electrode 152 and the second electrode 142. Since the electrode portion is in direct contact with the rear electric field portion 172, the contact resistance between the emitter portion 121 and the rear electric field portion 172 which are in contact with each other is reduced, so that the emitter portion 121 and the rear electric field portion are reduced. The charge transferred at 172 is more easily and stably collected.

The operation of the solar cell 11 having such a structure is as follows.

When light is irradiated onto the solar cell 11 and sequentially passes through the anti-reflection unit 130, the front electric field unit 171, and the front buffer unit 191 and enters the substrate 110, the substrate 110 may be caused by light energy. Electrons and holes are generated. At this time, since the surface of the substrate 110 is a texturing surface, the light reflectivity on the entire surface of the substrate 110 is reduced, and incident and reflection operations are performed on the texturing surface to increase light absorption, thereby improving efficiency of the solar cell 11. do. In addition, the reflection loss of the light incident on the substrate 110 by the anti-reflection unit 130 is reduced, so that the amount of light incident on the substrate 110 is further increased.

By pn junction of substrate 110 and emitter portion 121, holes pass through one of the first and second rear buffer portions 1921, 1922 (eg, first rear buffer portion 1921) Move toward the emitter portion 121 having a conductive type of electron type, and electrons pass through the other one of the first and second rear buffer portions 1921 and 1922 (eg, the second rear buffer portion 1922) It moves toward the rear electric field portion 172 having a conductivity type of. Electric charges moved to each emitter unit 121 and each rear electric field unit 172 are collected through the first and second auxiliary electrodes 151 and 152 to the first and second electrodes 141 and 142. When the first and second electrodes 141 and 142 are connected with a conductive wire, a current flows, which is used as power from the outside.

In this case, since the buffer parts 191 and 192 are positioned on the front and rear surfaces of the substrate 110, the surface of the substrate 110 or the vicinity of the substrate 110 may be due to a defect that exists near the front and rear surfaces and the front and rear surfaces of the substrate 110. The amount of charge lost at is reduced.

In addition, since the electric field parts 171 and 172 containing high concentrations of impurities of the same conductivity type as the substrate 110 are located on the front and rear surfaces of the substrate 110, the movement of the desired charge to the rear surface of the substrate 110 can be further improved. Easy to control As a result, electrons and holes are recombined and extinguished in the front and rear surfaces of the substrate 110 and in the vicinity thereof, and the efficiency of the solar cell 11 is improved.

In addition, due to the plurality of first and second auxiliary electrodes 151 and 152, the contact between the plurality of emitter parts 121 and the rear electric field part 172 and the plurality of first and second electrodes 141 and 142 may be used. Since the characteristic is improved, the efficiency of the solar cell 11 is further improved.

Also, the emitter part 121 and the rear electric field part 172 overlapping each other for the first rear buffer part 1921 in the overlapping portion between the adjacent emitter part 121 and the rear electric field part 172 overlapping each other. Are electrically and physically separated from each other.

This increases the design margin of the emitter portion 121 while realizing the insulation between the emitter portion 121 and the rear electric field portion 172.

In this case, a part of the thickness T2 of the first rear buffer part 1921 positioned between the emitter part 121 and the rear electric field part 172 overlapping each other is the first rear buffer part directly contacting the substrate 110 ( Thicker than the partial thickness T1 of 1921, the partial thickness T2 of the first rear buffer portion 1921 prevents the transfer of charge, thereby causing electrical interference between the superimposed emitter portion 121 and the rear electric field portion 172. To prevent. As a result, charge transfer between the emitter unit 121 and the rear electric field unit 172 superimposed on each other through the first rear buffer part 1921 is prevented, and thus the superimposed emitter unit 121 and the rear electric field unit 172 are prevented. Charge loss is prevented.

In addition, due to the energy bandgap difference due to the heterojunction between the substrate 110, the emitter unit 121, and the rear electric field units 171 and 172, the output voltage Voc of the solar cell 11 increases and thus the solar cell ( 11) increases the fill factor.

Next, another example of the present embodiment will be described with reference to FIG. 2.

In comparison with FIG. 1, the same reference numerals are assigned to components that perform the same function, and a detailed description thereof will be omitted.

Compared with FIG. 1, the solar cell 12 shown in FIG. 2 has an overlapping position between the emitter unit 121 and the rear electric field unit 172 and the overlapping position of the emitter unit 121 and the rear electric field unit 172. Except for the positions of the first and second rear buffer portions 1921 and 1922, it has the same structure as the solar cell 11 shown in FIG.

More specifically, the solar cell 11 of FIG. 1 has a portion of the first rear buffer portion 1921 positioned directly on the adjacent rear electric field portion 172 so that the first rear buffer portion 1921 is a rear electric field portion ( Some overlap with 172, whereby the emitter portion 121 located above the first rear buffer portion 1921 is positioned to partially overlap with the adjacent rear buffer portion 172 via the first rear buffer portion 1921. .

However, in the solar cell 12 of FIG. 2, in contrast to the solar cell 11 of FIG. 1, a portion of the second rear buffer portion 1922 is partially positioned directly above the upper portion of the adjacent emitter portion 121 so that the second rear buffer is formed. Portion 1922 partially overlaps emitter portion 121, and rear field portion 172 positioned over second rear buffer portion 1922 is adjacent emitter portion 121 with second rear buffer portion 1922 therebetween. ) And some overlap.

Thus, each second rear buffer portion 1922 is partially overlapped on an adjacent emitter portion 121, so that each second rear buffer portion 1922 is located up to a portion of the upper surface along the side of the adjacent emitter portion 121. .

As a result, a part of the second rear buffer portion 1922 exists between the emitter portion 121 and the rear electric field portion 172 overlapping each other.

Similar to those described with reference to FIGS. 1 and 2, some thicknesses T1 of the first rear buffer portion 1921 and the second rear buffer portion 1922 directly contacting the substrate 110 are the same, and The thickness T1 of these portions 1921 and 1922 is thinner than the thickness T2 of a portion of the second backside buffer portion 1922 located between the emitter portion 121 and the backside electric field portion 172 overlapping each other.

That is, since the charges moving from the substrate 110 must be moved toward the emitter portion 121 or the rear electric field portion 172 positioned thereon, the first rear buffer portion 1921 and the second rear surface which are in contact with the substrate 110. The buffer portion 1922 must have a thickness T1 through which charge can pass, and a part of the second rear buffer portion 1922 located between the emitter portion 121 and the rear electric field portion 172 overlapping each other. The thickness T2 should have a thickness T2 that can prevent the movement of the charge moved to the emitter portion 121 and the charge moved to the backside electric field 172 at the overlapped portion.

Accordingly, the thickness T1 of the first rear buffer portion 1921 and the second rear buffer portion 1922, which is in contact with the substrate 110, may be about 1 nm to 10 nm, and may overlap with the overlapped emitter portion 121. The thickness T2 of the second rear buffer portion 1922 located between the rear electric field portions 172 may be about 10 nm to about 200 nm.

In this example, the lower surface of the emitter portion 121 is a surface in contact with the first rear buffer portion 1921, and the upper surface of the emitter portion 121 is a surface opposite to the lower surface and the first auxiliary electrode 151. This is the side that is facing. In this case, the width W4 of the second rear buffer portion 1922 overlapping the emitter part 121 may be 5 μm or more and less than 1/2 of the width W2 of each emitter part 121.

As a result, by the second rear buffer portion 1922 partially positioned on the adjacent emitter portion 121, each rear electric field portion 172 is stable and overlaps with the adjacent emitter portion 121 while maintaining electrical insulation. To be located.

Therefore, when the plurality of emitter portions 121 are formed and then the plurality of rear electric field portions 172 are formed, the rear electric field portions 172 may be designed to overlap with the adjacent emitter portions 121. The design margin of the electric field unit 172 is increased, and electrical insulation between the overlapped emitter unit 121 and the rear electric field unit 172 is stable, and is located between the emitter unit 121 and the rear electric field unit 172. Charge transfer that occurs through the second backside buffer portion 1922 is prevented, thereby reducing the recombination loss of charge.

When the width W4 of the second rear buffer portion 1922 overlapping the rear electric field portion 172 is 5 μm or more, the design margin of the rear electric field portion 172 positioned on the emitter portion 121 is stably increased. When the width W4 of the second rear buffer portion 1922 overlapping the emitter portion 121 is less than or equal to 1/2 of the width W1 of each emitter portion 121, the upper portion of the second rear buffer portion 1922 is positioned on the emitter portion 121. The first electrode part is stably positioned.

Next, referring to FIGS. 4 and 5, an example of a solar cell according to an exemplary embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to components that perform the same functions as FIGS. 1 to 3, and detailed description thereof will be omitted.

First, an example of a solar cell according to the present embodiment will be described with reference to FIG. 4.

In the solar cell 13 illustrated in FIG. 4, the thickness of the first portion of the substrate 110a in which the plurality of emitter portions 121 are positioned and the second portion of the substrate 110a in which the plurality of rear electric fields 172 are located 1, except that the plurality of first electrode portions positioned on the plurality of emitter portions 121 and the plurality of second electrode portions positioned on the plurality of rear electric field portions 172 are different from each other. It has the same structure as one solar cell 11.

Therefore, only the different parts compared with the solar cell 11 of FIG. 1 are demonstrated in detail.

As shown in FIGS. 4 and 5, the substrate 110a has a flat surface as shown in FIGS. 1 and 2, but has a plurality of emitter portions 121 and a plurality of rear electric field portions 172. The rear surface of the substrate 110 on which is formed has a recess and a protrusion. Therefore, the thickness of the substrate 110 varies depending on the position.

Therefore, a plurality of first portions having a first thickness D1 of the substrate 110 and a plurality of second portions having a second thickness D2 different from the first thickness D1 are provided.

As a result, the rear surface of the substrate 110a having no texturing surface is not a plane having substantially the same thickness as the position change but a plurality of protrusions (the plurality of second portions) and the plurality of protrusions whose thickness is substantially changed as the position change. It is a non-planar surface having a recessed portion (a plurality of first portions), whereby the rear surface of the substrate 110a has a first thickness D1 and a second thickness D2 in accordance with the positional change.

In this example, when at least one of the front and rear surfaces of the substrate 110 has a textured surface formed by the texturing process, the thickness difference of the substrate 110a caused by the irregularities formed on the textured surface is substantially the same. Consider.

Thus, when the back surface of the substrate 110 has a texturing surface formed by a texturing process, each first back buffer portion 1921 at a plurality of first portions having a first thickness and in which a plurality of emitter portions 121 are located. The surface of each first portion in contact with) has a texturing surface.

In addition, in the plurality of second portions having a second thickness different from the first thickness and in which the plurality of rear electric field portions 172 are located, the surface of each second portion in contact with each second rear buffer portion 1922 is also textured. You have a surface. Therefore, when thicknesses having different sizes exist within a range of thickness differences caused by uneven surfaces formed on the texturing surface on the back surface of the substrate 110a, these thicknesses are considered to be the same. Similarly, when the front surface of the substrate 110a also has a texturing surface, the different thicknesses present within the thickness difference range generated by the front surface of the substrate 110a or the uneven surface formed on the textured surface formed on the front and rear surfaces are the same. Consider.

In the solar cell 13 illustrated in FIG. 4, the thickness D1 of the first part where the emitter part 121 is located is thinner than the thickness D2 of the second part where the rear electric field part 172 is located, and FIG. 5. In the solar cell 14 illustrated in FIG. 3, the thickness D1 of the first part where the emitter part 121 is located is thicker than the thickness D2 of the second part where the rear electric field part 172 is located.

In the case of FIG. 4, as shown in FIGS. 1 and 2, the first rear buffer portion 1921 and the emitter portion 121 positioned thereon are partially positioned on the adjacent rear electric field portion 172, and in FIG. 5, FIG. 3. As such, the second rear buffer portion 1922 and the rear electric field 172 positioned thereon are partially positioned on the adjacent emitter portion 121.

Thus, in FIG. 4, the first backside buffer portion 1921 located in the first portion of the substrate 110 having the low thickness D1 is formed on the first portion and the second side on the backside of the first portion of the substrate 110. Along the side of the substrate 110 exposed by the stepped portion of the portion extends to the upper portion of the upper portion of the adjacent rear field portion 172, the emitter portion 121 is a first over the upper portion of the first rear buffer portion 1921 It is positioned in the same plane shape as the rear buffer portion 1921.

In addition, in FIG. 5, the second rear buffer portion 1922 located in the second portion of the substrate 110 having the low thickness D2 is formed on the first portion and the second portion on the rear surface of the second portion of the substrate 110. Along the side of the substrate 110 exposed by the stepped portion of the portion extends to the upper portion of the upper portion of the adjacent emitter portion 121, the rear electric field portion 172 is a second over the top of the second rear buffer portion 1922 It is located in the same planar shape as the rear buffer portion 1922.

However, in contrast to FIG. 4, as shown in FIG. 2, the second rear buffer portion 1922 and the rear electric field 172 positioned thereon may be partially positioned on the adjacent emitter portion 121, and FIG. 5. 1 and 2, the first rear buffer portion 1921 and the emitter portion 121 positioned thereon may be partially positioned on the adjacent rear electric field portion 172.

As such, as shown in FIG. 4, the thickness D1 of the first portion of the substrate 110a, that is, the surface (front) and the first rear buffer portion 1921 of the substrate 110a in contact with the front buffer portion 191. The shortest distance between the surface (rear surface) of the substrate 110a in contact with the thickness D2 of the second portion of the substrate 110a, that is, the surface of the substrate 110a in contact with the front buffer portion 191 and the second rear surface. If less than the shortest distance between the surface of the substrate 110a in contact with the buffer portion 1922, the shortest distance from the front surface of the substrate 110a to the emitter portion 121 that collects holes is electrons from the front surface of the substrate 110a. It will be shorter than the shortest distance to the rear electric field 172 to collect.

As a result, the movement distance of the holes located on the front surface or the portion of the substrate 110 is shorter than the movement distance of the electrons, thereby increasing the amount of holes moving to the emitter portion 121, thereby improving the efficiency of the solar cell 13. do.

In general, since the mobility of holes is slower than electrons, when each emitter part 121 and each rear electric field part 172 are located at the same thickness from the front of the substrate 110, the emitter part 121 and the rear electric field are respectively. The time difference between the holes and the electrons reaching the step 172 occurs. That is, the speed of the holes reaching up to the p-type emitter part 121 is slower than the speed of the electrons reaching up to the n-type rear electric field part 172, which is greater than the amount of holes reaching each emitter part 121 for the same time. The amount of electrons reaching each rear electric field 172 becomes large.

For this reason, unlike the present embodiment, the thickness of the substrate 110 is the same regardless of the position, the emitter portion 121 and the rear electric field portion 172 is located at a position having the same thickness from the front of the substrate 110. In the comparative example, the amount of electrons reaching each rear electric field 172 is greater than the amount of holes reaching each emitter 121 during the same time, and also moves toward the emitter 121 due to a slow moving speed. The amount of holes lost during the movement is greater than the amount of electrons lost during the movement toward the rear electric field 172, and the amount of holes moved toward each emitter 121 moves toward each rear electric field 172. Less than the amount of electrons.

However, as shown in FIG. 4 of the present example, by varying the thickness of the substrate 110 according to the position, the thickness D1 between the emitters 121 from the front of the substrate 110 is changed from the front of the substrate 110 to the rear of the substrate 110. When the thickness D2 between the electric field parts 172 is thinner, the amount of holes moving to each emitter part 121 increases for the same time as in the comparative example described above, and also moves to each emitter part 121. The amount of holes lost also decreases, and the amount of holes moved to each emitter part 121 increases.

In this case, the thickness D1 of the first part may be 100 μm to 150 μm, and the thickness D2 of the second part may be 200 μm to 250 μm.

In this case, when the substrate thickness D1 of the first portion (eg, the emitter portion) where the p-type impurity portion is located is 100 μm or more, the movement distance of the hole may be more effectively compensated for the difference in the movement speed between the hole and the electron. It is possible to more efficiently compensate for the difference in the moving speed between the holes and the electrons. The amount of electrons can be further reduced to further reduce the amount of recombination of holes and electrons moving to the p-type impurity portion.

In addition, when the substrate thickness D2 of the second portion (eg, the rear electric field portion) in which the n-type impurity portion is located is 200 μm or more, an amount of electric charge more suitable for the operation of the solar cell 13 is generated, and When the substrate thickness D2 is 250 μm or less, the movement distance of the charge is further reduced to further reduce the amount of charge lost while moving to the desired position.

However, on the contrary, as shown in FIG. 5, when the thickness D1 of the first portion of the substrate 110a is larger than the thickness D2 of the second portion of the substrate 110a, electrons are drawn from the front surface of the substrate 110a. The shortest distance to the rear electric field unit 172 to collect is shorter than the shortest distance from the front surface of the substrate 110a to the emitter unit 121 to collect holes. Accordingly, the thickness D1 of the first part of FIG. 5 may be the same as the thickness D2 of the second part of FIG. 4, and the thickness D2 of the second part of FIG. 5 may be the same as that of the first part of FIG. 3. It may be the same as the thickness (D1). For example, the thickness D2 of the second portion of the substrate 110a on which each of the rear electric fields 172 is located is about 100 μm to 150 μm, and the first portion of the substrate 110a on which each emitter 121 is located. The thickness D1 of the portion may be about 200 μm to 250 μm.

For this reason, in FIG. 4, the p-type impurity portion is located in the portion of the substrate 110a having the thin thickness D1 (that is, the first portion), and the portion of the substrate 110a having the thick thickness D2 (that is, in FIG. 4). The n-type impurity portion is located in the second portion), but in FIG. 5, the n-type impurity portion is located in the portion (eg, the second portion) of the substrate 110 having the thin thickness D2 and has a thick thickness D1. The p-type impurity portion is positioned in a portion (eg, the first portion) of the substrate 110.

Therefore, the moving distance of the electrons moving to each of the rear electric field parts 172 is smaller than the moving distance of the holes moving to each emitter part 121.

As a result, when compared with the comparative example in which the plurality of emitter portions and the plurality of rear electric field portions are located at portions having the same thickness from the front surface of the substrate 110a, the movement distance of each electron moving to each rear electric field portion 172 is reduced. . Since the movement distance of the electrons is reduced, the probability of electrons being captured by defects such as dangling bonds present in the substrate 110a is reduced when the electrons move through the substrate 110a to the rear electric field 172. do. Therefore, the amount of electrons that move to each backside electric field 172 increases compared to the comparative example.

At this time, since the electron moving speed in the substrate 110 is faster than the hole moving speed, in order to compensate not only the moving speed of the electrons faster than the holes but also the reduced moving distance due to the thickness difference of the substrate 110, For example, the width W21 of each emitter portion 121, which is a p-type impurity facing the rear surface of the substrate 110, is each rear electric field portion 172, which is an n-type impurity portion facing the rear surface of the substrate 110. It may have a width larger than the width W22. Therefore, since the width W21 of the emitter portion 121 for collecting holes with low mobility is larger than the width W22 of the rear electric field portion 172 for collecting electrons, the amount of holes collected increases, so that the substrate ( Another difference is compensated for the amount of electrons and holes collected due to the thicknesses D1 and D2 of 110a).

As described above, when the back surface of the substrate 110a is stepped between the first and second portions, the first auxiliary electrode 151 positioned on the portion (first portion or second portion) having a relatively small thickness. Alternatively, the second auxiliary electrode 152 may have a thickness thicker than that of the other second auxiliary electrode 152 or the first auxiliary electrode 151. As a result, since the difference in height between the first electrode portion and the second electrode portion of the solar cells 13 and 14 generated due to the step of the substrate 110a is compensated for, the plurality of solar cells may be electrically conductive, such as ribbons. When manufacturing a solar cell module by electrically connecting in series or parallel manner using a tape, manufacture of a solar cell module is performed easily.

However, in an alternative example, in FIGS. 4 and 5, the first auxiliary electrode 151 or the second auxiliary electrode 152 positioned over the portion (first portion or second portion) having a relatively small thickness may be It may have the same thickness as the other second auxiliary electrode 152 or the first auxiliary electrode 151. In this case, manufacturing time and manufacturing cost of the first and second auxiliary electrodes 151 and 152 are reduced.

Next, a solar cell according to another embodiment of the present invention will be described with reference to FIGS. 6 and 7.

Comparing the solar cells 15, 16 shown in FIGS. 6 and 7 and the solar cells 11, 12 shown in FIGS. 1, 2, and 3, respectively, the back of the solar cells 15 overlapping each other. An insulating film 181 made of an insulator is further disposed between the electric field part 172 and the first rear buffer part 1921 (FIG. 6), or a part of the emitter part 121 overlapping each other in the solar cell 16. An insulating film 181 made of an insulator is further positioned between the second back buffer portion 1922 and the second back buffer portion 1922 (FIG. 7).

The insulating film 181 of FIG. 6 extends in the extending direction of the rear electric field 171 between the portion of the rear electric field portion 171 and the first rear buffer portion 1921 that are in contact with each other, and the insulating film 181 of FIG. An extended portion of the emitter portion 121 extends between the emitter portion 121 and the second rear buffer portion 1922 that are in contact with each other.

The insulating layer 181 may be formed of an insulating material different from that of the first and second rear buffer parts 192. For example, the insulating layer 181 may be formed of an insulating material such as silicon oxide based (eg, SiOx, a-SiOx, SiOx: H, a-SiOx: H), or silicon nitride based (eg, SiNx). The thickness of the insulating layer 181 may be about 10 nm to several hundred nm, for example, about 10 nm to 200 nm.

In this case, the first rear buffer portion 1921 and the second rear buffer portion 1922 have a thickness T1 that is substantially the same regardless of the position, and the thickness T1 at this time is capable of moving charges as described above. It is about the thickness. Accordingly, the thickness T1 of each of the first rear buffer portion 1921 and the second rear buffer portion 1922 may be about 1 nm to 10 nm.

As described above, the insulating layer 181 is additionally disposed in addition to the first rear buffer portion 1921 or the second rear buffer portion 1922 at a portion where the emitter portion 121 and the rear electric field portion 172 overlap each other. Since the electrical insulation is performed between the overlapping emitter part 121 and the rear electric field part 172 together with the first rear buffer part 1921 or the second rear buffer part 1922, the emitter part overlapping each other ( Electrical insulation between 121 and the back field 172 is made more stable.

At this time, by the insulating film 181 located between the overlapped emitter portion 121 and the rear electric field portion 172, the electrical interference between the emitter portion 121 and the rear electric field portion 172 at the overlapped portion reliably. As an alternative, in an alternative example, there is no first back buffer portion 1921 or a second back buffer portion 1922 between the superimposed emitter portion 121 and the back electric field portion 172 or FIGS. In contrast to 3, the first rear surface is disposed between the emitter portion 121 and the rear electric field portion 172 overlapping the thicknesses of the first rear buffer portion 1921 and the second rear buffer portion 1922 that are in contact with the substrate 110. The buffer portion 1921 or the second rear buffer portion 1922 may have a thin thickness.

As a result, the emitter unit 121 and the rear electric field unit overlapping through the first or second rear buffer portions 1921 and 1922 positioned between the emitter unit 121 and the rear electric field unit 172 overlapping each other ( Since the electrons and the hole movement between the 172 is prevented, the loss of the solar cell 15 is reduced by preventing the recombination loss of electrons and holes generated in the overlapping portion of the emitter unit 121 and the rear electric field unit 172.

6 and 7, the insulating layer 181 is positioned between the rear electric field part 172 and the first rear buffer part 1921 overlapping each other (FIG. 6), or the emitter part 121 overlapping each other. Located between the second backside buffer portions 1922 (FIG. 7).

However, the second rear buffer portion 1921 and the emitter portion 121 overlapping each other on the rear electric field portion 172 or overlapping each other on the emitter portion 121 are different from each other. It may be located between the 1922 and the rear electric field (172). In this case, only the position of the insulating film 181 is changed, and the role of the insulating film 181 is also described with reference to FIGS. 6 and 7, as described above with reference to FIGS. 6 and 7. More stable insulation.

Next, another example according to another embodiment of the present invention will be described with reference to FIGS. 8 and 9.

The solar cells 17 and 18 shown in FIG. 8 and FIG. 9, respectively, have an insulating film 182 like the solar cells 15 and 16 shown in FIGS. 6 and 7, respectively.

However, the formation positions of the insulating film 181 shown in FIG. 6 and FIG. 7 and the insulating film 182 of this example differ from each other.

That is, as shown in FIG. 8, the insulating film 182 is formed on the back of the substrate 110 between the adjacent first rear buffer portion 1921 and the second rear buffer portion 1922, and the adjacent second rear buffer portion ( It is located on the side of 1922 and on the side of the backside electric field 172 located above the second backside buffer portion 1922 and over the top portion of the adjacent backside electric field 172. As a result, the first rear buffer portion 1921 and the second rear buffer portion 1922 positioned directly on the rear surface of the substrate 110 are not directly in contact with the rear surface of the substrate 110, but are spaced at a predetermined interval and are arranged side by side in a predetermined direction. Stretched.

As a result, the first rear buffer portion 1921 may be formed on the insulating layer 182 immediately above the rear surface of the substrate 110 where the second rear buffer portion 1922 and the insulating layer 182 are not located, and along the adjacent insulating layer 182. The emitter portion 121 is positioned above the first rear buffer portion 1921.

At this time, the first rear buffer portion 1921 and the emitter portion 121 positioned thereon have the same planar shape, but the first rear buffer portion 1921 and the emitter portion 121 positioned thereon are positioned at the lower portion thereof. It has a planar shape different from the insulating film 182.

For example, as shown in FIG. 8, since the first rear buffer portion 1921 is not positioned on a portion of the insulating layer 182 positioned on the upper surface of the rear electric field unit 172, the upper portion of the insulating layer 182 is not included. Is exposed without being applied by the first rear buffer portion 1921 and the emitter portion 121, or as shown in FIG. 9, on a portion of the insulating film 182 positioned on the upper surface of the emitter portion 121. Since the second rear buffer portion 1922 is not located, the upper portion of the insulating layer 182 is exposed without being applied by the second rear buffer portion 1922 and the rear electric field portion 172.

As such, the design margin of the emitter portion 121 and the rear electric field portion 172 positioned on the insulating film 182 on the upper portion of the rear electric field portion 172 or the emitter portion 121 increases. As a result, the emitter portion 121 and the rear electric field portion 172 positioned on the insulating film 182 are formed over the rear electric field portion 172 or the emitter portion 121 beyond the formation position of the insulating film 182, A short phenomenon between the rotor part 121 and the rear electric field part 172 is prevented to prevent charge loss in the emitter part 121 and the rear electric field part 172 which are in contact with each other.

In addition, compared to the insulating film 181 of FIGS. 6 and 7, the insulating film 182 of FIGS. 8 and 9 may have a substrate 110 between an adjacent first rear buffer portion 1921 and a second rear buffer portion 1922. And further adjacent insulation between the first rear buffer portion 1921 and the second rear buffer portion 1922 adjacent to each other as it is further positioned directly above the rear and between the adjacent emitter portion 121 and the rear electric field portion 172. Insulation operation between the rotor part 121 and the rear electric field part 172 is made more stable. Accordingly, different types of charges (holes and electrons) passing through the first rear buffer portion 1921 and the second rear buffer portion 1922 respectively are formed in the first rear buffer portion 1921 and the second rear buffer portion 1922. The problem of being lost at the contact portion of is prevented or reduced, and the insulation state between the emitter portion 121 and the rear electric field portion 172 adjacent to each other is more surely maintained.

6 to 9 of the present embodiment have been applied to a solar cell having a substrate 110 having substantially the same thickness according to the position as shown in Figs. As shown in FIGS. 4 and 5, a plurality of emitter portions 121 are disposed on portions of the substrate 110 having the first thickness on the substrate 110a having different thicknesses (eg, the first thickness and the second thickness) according to positions. It is, of course, also applicable to a solar cell which locates and positions the plurality of backside electric fields 172 on a portion of the substrate 110 having a second thickness.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

11-18: solar cell 110, 110a: substrate
121: emitter portion 130: antireflection portion
141 and 142 main electrode 151 and 152 auxiliary electrode
171: front electric field 172: rear electric field
191: front buffer portion 192: rear buffer portion
1921 and 1922 back buffer portions 181 and 182 insulating film

Claims

A substrate made of a crystalline semiconductor and having a first conductivity type,
A first buffer portion located directly on the first side of the substrate and composed of amorphous silicon,
A second buffer portion located directly on the first side of the substrate and composed of amorphous silicon,
An emitter portion disposed on the first buffer portion and formed of an amorphous semiconductor, the emitter portion having a second conductivity type different from the first conductivity type,
A first electric field part disposed on the second buffer part and made of an amorphous semiconductor, the first electric field part having the first conductivity type,
A first electrode portion located directly on the emitter portion, and
A second electrode part directly positioned on the first electric field part
Including,
A part of the emitter part and a part of the rear electric field part overlap each other,
The first buffer portion or the second buffer portion is further located between the overlapping emitter portion and the backside electric field portion.
Solar cells.

In claim 1,
The first thickness of the first buffer portion or the second buffer portion located between the overlapping emitter portion and the backside electric field portion is equal to that of the first buffer portion or the second buffer portion located on the first surface of the substrate. A solar cell thicker than the second thickness.

In claim 2,
The first thickness is 1 nm to 10 nm, and the second thickness is 10 nm to 200 nm.

In claim 1,
And the first buffer portion and the second buffer portion are made of amorphous silicon.

In claim 1,
And the emitter portion and the first electric field portion are separated from each other.

6. The method according to any one of claims 1 to 5,
The substrate includes a first portion and a second portion having different thicknesses.

The method of claim 6,
One of the emitter portion and the first electric field portion is positioned on the first portion,
And the other of the emitter portion and the first electric field portion is positioned on the second portion.

The method of claim 6,
The thickness of the first portion is 100 μm to 150 μm, and the thickness of the second portion is 200 μm to 250 μm.

In claim 1,
And overlapping the first buffer portion or the second buffer portion with the insulating layer interposed between the emitter portion and the first electric field portion.

The method of claim 9,
The insulating layer is a solar cell located directly above one of the emitter portion and the first electric field portion.

11. The method of claim 10,
And the insulating layer is positioned between the first electric field portion and the first buffer portion overlapping each other or between the emitter portion and the second buffer portion overlapping each other.

11. The method of claim 10,
And the insulating layer is positioned between the first buffer portion and the emitter portion overlapping each other or between the second buffer portion and the first electric field portion overlapping each other.

The method of claim 9,
The thickness of the first buffer portion or the second buffer portion located between the overlapping emitter portion and the backside electric field portion is equal to the thickness of the first buffer portion or the second buffer portion located on the first surface of the substrate. Same solar cell.

The method of claim 9,
The thickness of the insulating film is a solar cell 10nm to 200nm.

The method according to any one of claims 9 to 14,
The first buffer portion and the first buffer portion are separated from each other,
The insulating film is directly over a portion of the first surface of the substrate exposed between the first buffer portion and the second buffer portion, and between the side of the emitter portion and the second buffer portion or the side of the first electric field portion. And a solar cell further located between the first buffer portion.

16. The method of claim 15,
The substrate includes a first portion and a second portion having different thicknesses.

17. The method of claim 16,
One of the emitter portion and the first electric field portion is positioned on the first portion,
And the other of the emitter portion and the first electric field portion is positioned on the second portion.

17. The method of claim 16,
The thickness of the first portion is 100 μm to 150 μm, and the thickness of the second portion is 200 μm to 250 μm.

6. The method according to any one of claims 1 to 5,
And a buffer unit formed of an amorphous semiconductor on the second surface of the substrate opposite the first surface.

In claim 1,
And a second electric field portion made of an amorphous semiconductor and having the first conductivity type on a second surface of the substrate, which is opposite the first surface.