KR102126851B1 - Solar cell and manufacturing method thereof - Google Patents

Abstract

The solar cell includes a substrate having a first conductivity type; An emitter portion located on the front surface of the substrate and having a second conductivity type opposite to the first conductivity type; A first electrode electrically connected to the emitter portion; A plurality of local backside electric field portions located locally on the back side of the substrate and containing impurities of a first conductivity type in a higher concentration than the semiconductor substrate; A second electrode electrically connected to the plurality of local rear electric fields; A protective film formed on a front surface, a back surface, and both side surfaces of the semiconductor substrate in a region where the first electrode and the second electrode are not located, and formed of a material having a fixed charge having the same polarity as the first conductivity type; And a plurality of insulating portions electrically insulating the emitter portion and the local rear electric field portion, wherein the plurality of insulating portions are positioned between the high concentration doping portion and the high concentration doping portion and the protective film containing impurities of the first conductivity type in a higher concentration than the semiconductor substrate. It is formed including a depletion region.

Description

SOLAR CELL AND MANUFACTURING METHOD THEREOF

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

Recently, as the depletion of existing energy resources such as petroleum or coal is predicted, interest in alternative energy to replace them is increasing, and accordingly, solar cells that produce electric energy from solar energy are attracting attention.

A typical solar cell includes a semiconductor portion 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 enters the solar cell, electric charges (electrons and holes) are generated in the semiconductor, and the generated charges move to the n-type and p-type semiconductors by pn junction, respectively, so the electrons move toward the n-type semiconductor portion and the holes are Move toward the p-type semiconductor portion.

And the moved electrons and holes are collected by different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively.

Technical problem to be achieved by the present invention is to provide a solar cell with improved efficiency and a method for manufacturing the same.

A solar cell according to an aspect of the present invention includes a substrate having a first conductivity type; An emitter portion located on the front surface of the substrate and having a second conductivity type opposite to the first conductivity type; A first electrode electrically connected to the emitter portion; A plurality of local backside electric field portions located locally on the back side of the substrate and containing impurities of a first conductivity type in a higher concentration than the semiconductor substrate; A second electrode electrically connected to the plurality of local rear electric fields; A protective film formed on a front surface, a back surface, and both side surfaces of the semiconductor substrate in a region where the first electrode and the second electrode are not located, and formed of a material having a fixed charge having the same polarity as the first conductivity type; And a plurality of insulating portions electrically insulating the emitter portion and the local rear electric field portion, wherein the plurality of insulating portions are positioned between the high concentration doping portion and the high concentration doping portion and the protective film containing impurities of the first conductivity type in a higher concentration than the semiconductor substrate. This includes the depletion region.

Here, it is preferable that the plurality of insulating portions are located on the rear surface of the semiconductor substrate.

The second electrode is positioned in an area overlapping the local rear electric field, and the width of the second electrode is smaller than the width of the local rear electric field.

The plurality of local rear electric field units may include a contact region contacting the second electrode; And a margin area excluding the contact area.

The margin region is formed as a depletion region, and the width of the contact region and the width of the margin region are formed equal to each other.

The protective layer includes aluminum oxide (AlO _x ) having a negative fixed charge, and further includes an anti-reflection layer positioned on the protective layer.

The antireflection film is formed of silicon nitride having a positive (+) fixed charge.

The solar cell having such a configuration includes forming an emitter portion on a front surface of a semiconductor substrate; Forming a plurality of local back surface electric fields and a plurality of insulating parts on the back surface of the semiconductor substrate; Forming protective films on front, back, and both sides of the semiconductor substrate; And forming a front electrode positioned on the front surface of the substrate and connected to the emitter portion, and a rear electrode positioned on the rear surface of the substrate and connected to the plurality of local rear electric field portions, wherein the plurality of insulating portions contain impurities of the first conductivity type. It can be manufactured by a manufacturing method including a high-concentration doped portion containing a high concentration and a depletion region located between the high-concentration doped portion and a protective film compared to a semiconductor substrate.

Here, the forming of the plurality of local back surface electric fields and the plurality of insulating parts may include: forming an impurity layer on the back surface of the semiconductor substrate; And forming the impurity layer according to the step of locally irradiating the laser.

The protective film is preferably formed on the entire surface of the substrate using atomic layer deposition (ALD).

According to this feature, the present invention is to form aluminum oxide (AlO _x ) on the entire surface of the substrate by atomic layer deposition (ALD), and use it as a protective film, thereby lowering the interface trap density of aluminum oxide (interface) It is possible to obtain a chemical passivation characteristic according to trap density) and a field effect passivation characteristic by a negative (-) fixed charge, and improve stability, moisture permeability, and wear resistance characteristics.

In addition, electrodes of different polarities formed on the front and rear surfaces of the substrate are electrically connected through an inversion layer formed on the inside and side surfaces of the rear surface of the substrate by the negative (-) fixed charge of the protective film. By forming an isolation pattern on the back side of the substrate to prevent the light incident surface, that is, the front surface of the substrate can be utilized as much as possible, the amount of light incident on the substrate can be increased. It is possible to effectively prevent electric charges collected from the back side from moving toward the front side of the substrate.

In addition, the present invention can form a local back surface field (LBSF) by irradiating a laser on the back surface of the substrate, thereby reducing the contact resistance between the substrate and the back electrode and reducing the recombination rate of electrons and holes.

And, when the LBSF is formed by irradiating a laser, the present invention can insulate the front and rear surfaces of the substrate without further processing by forming an insulating pattern by the laser. Therefore, the efficiency of a solar cell can be improved.

1 is a schematic cross-sectional view of a solar cell according to a first embodiment of the present invention.
2A to 2I are views sequentially illustrating a method of manufacturing a solar cell according to a first embodiment of the present invention.
3 is a schematic cross-sectional view of a solar cell according to a second embodiment of the present invention.
4 is a schematic cross-sectional view of a solar cell according to a third embodiment of the present invention.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. This is not intended to limit the present invention to specific embodiments, and can be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. The terms may be used only for the purpose of distinguishing one component from other components.

For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component.

The term “and/or” can include a combination of a plurality of related described items or any of a plurality of related described items.

When a component is said to be "connected" or "coupled" to another component, it may be directly connected to or coupled to the other component, but other components may exist in the middle. Can be understood.

On the other hand, when a component is said to be "directly connected" or "directly coupled" to another component, it can be understood that no other component exists in the middle.

The terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

In this application, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and one or more other features. It can be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

In the drawings, the thickness is enlarged to clearly express various layers and regions. When a portion of a layer, film, region, plate, or the like is said to be “above” another portion, this includes not only the case “directly above” the other portion, but also the case where there is another portion in between. Conversely, when one part is "just above" another part, it means that there is no other part in the middle.

Unless defined otherwise, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains.

Terms, such as those defined in a commonly used dictionary, can be interpreted as having meanings that are consistent with meanings in the context of related technologies, and are interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. It may not be.

In addition, the following embodiments are provided to more fully explain to those having average knowledge in the art, and the shapes and sizes of elements in the drawings may be exaggerated for more clear explanation.

Then, embodiments of the present invention will be described with reference to the accompanying drawings.

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

Referring to FIG. 1, the solar cell according to the first embodiment of the present invention includes an emitter region located on a front surface (first surface) of a substrate 110 and a substrate 110 to which light is incident. ) 120, and the entire surface of the substrate 110, that is, the protective film 130 located on the front, back and side surfaces, the first anti-reflection film 140 located on the front of the substrate 110 and positioned on the protective film 130 , A front electrode 150 positioned on the front surface of the substrate 110 and positioned on the emitter portion 120 in a region where the protective layer 130 and the first anti-reflection layer 140 are not located, and a back surface of the substrate 110 ) (Second side) local back surface field portion (Local Back Surface Field Portion) 160, located in the back of the substrate 110, the insulating portion 162, located on the back of the substrate 110 and the protective film The rear electrode 170 positioned on the rear surface of the plurality of local rear electric field parts 160 in a region where the second anti-reflection layer 142, the protective layer 130, and the second anti-reflection layer 142 are positioned on the 130 side. ).

The substrate 110 is a semiconductor substrate made of a semiconductor such as silicon of a first conductivity type, for example, an n-type conductivity type. At this time, the semiconductor is a crystalline semiconductor made of single crystal silicon. The n-type substrate 110 is doped with impurities of a pentavalent element such as phosphorus (P), arsenic (As), and antimony (Sb).

The front surface of the substrate 110 has a textured surface having a plurality of protrusions and a plurality of uneven surfaces. Accordingly, the emitter portion 120, the protective layer 130, and the first anti-reflection layer 140 located on the front surface of the substrate 110 also have a texturing surface.

At this time, the texturing surface may be formed through a separate process performed on the flat surface of the substrate 110. For example, the texturing surface removes a damage layer caused by a slicing process performed to fabricate a substrate for a solar cell from a silicon ingot using hydrogen fluoride (HF) or the like. After the damage layer removal process (saw damage removing process) or after completing the damage layer removal process may be formed through a texturing process performed through dry etching or wet etching.

As described above, when the front surface of the substrate 110 has a textured surface through a separate process, the incident area of the substrate 110 increases and the light reflectivity decreases due to a plurality of reflection operations due to unevenness, so that the substrate 110 Since the amount of incident light increases, the efficiency of the solar cell is improved.

The emitter part 120 is an impurity doping part in which impurities of a second conductivity type, for example, a p-type conductivity type, doped with the substrate 110, which is opposite to the conductivity type of the substrate 110, is a surface on which light is incident. That is, it is located on the front surface of the substrate 110. Therefore, the second conductive type emitter portion 120 forms a p-n junction with the substrate 110, that is, the first conductive type portion.

Due to the built-in potential difference due to the pn junction, electrons and holes, which are charges generated by light incident on the substrate 110, move in the corresponding direction, that is, electrons move toward the n-type and the holes Move toward p-type. Therefore, when the substrate 110 is n-type and the emitter portion 120 is p-type, the separated electrons move toward the substrate 110 and the separated holes move toward the emitter portion 120. In the substrate 110, electrons become a large number of charges, and in the emitter unit 120, holes become a large number of charges.

When the emitter portion 120 has a p-type conductivity type, the emitter portion 120 is doped with impurities of a trivalent element such as boron (B), gallium (Ga), and indium (In) to the substrate 110 Can form.

The protective layer 130 is located on the entire surface of the substrate 110 except for the portion where the front electrode 150 and the rear electrode 170 are located, and is made of a material having a negative fixed charge. For example, it may be made of aluminum oxide (AlO _x ), may have a refractive index of 1.55 to 1.7, and a thickness of 5 to 30 nm.

At this time, the protective film 130 made of aluminum oxide (AlO _x ) is formed by an atomic layer deposition (ALD) method with good step coverage.

A positive (+) charge hole is pulled toward the emitter part 120 by the protective film 130 of aluminum oxide (AlO _x ) having a negative (-) fixed charge located on the p-type emitter part 120, and the negative ( -) The electrons that are charged generate an electric field passivation effect that is pushed toward the rear side of the substrate 110. That is, due to the protective layer 130 of aluminum oxide (AlO _x ), the amount of holes moving toward the emitter portion 120 is further increased, but the amount of electrons moving toward the emitter portion 120 decreases, so that the emitter portion 120 The amount of recombination of electrons and holes decreases.

In addition, the oxygen (O) contained in the aluminum oxide (AlO _x ) moves toward the surface of the substrate 110 in contact with the protective film 130 and dangling bonds present on and near the surface of the substrate 110 ) Performs a surface passivation function that turns defects into stable bonds.

As such, the passivation layer 130 may obtain chemical passivation characteristics according to low interface trap density of aluminum oxide (AlO _x ) and field effect passivation characteristics due to negative (-) fixed charge, stability, The moisture permeability and abrasion resistance characteristics can be improved. Therefore, it is possible to improve the efficiency of the solar cell by reducing the rate of recombination of charges on the surface of the substrate 110 and improve long-term reliability.

Meanwhile, an inversion layer 10 is formed inside the back surface and inside the side surface of the substrate 110 by the negative (-) fixed charge of the protective film 130.

The first anti-reflection layer 140 is positioned only on the protective layer 130 located on the front surface of the substrate 110 and not on the portion where the front electrode 150 is located. The first anti-reflection film 140 is made of a material having a positive (+) fixed charge that prevents light reflection and transmits light of the substrate 110. For example, it may be made of hydrogenated silicon nitride (SiNx:H), and may have a refractive index of 1.9 to 2.3 and a thickness of 50 nm to 100 nm.

Hydrogen (H) contained in the first anti-reflection film 140 moves to the surface of the substrate 110 via the protective film 130 to perform a passivation function on and near the surface of the substrate 110, and the substrate 110 The efficiency of the solar cell is increased by reducing the reflectivity of light incident through the front surface and increasing the selectivity of a specific wavelength region.

Therefore, by the passivation function by the first anti-reflection film 140 as well as the protective film 130, the amount of charges lost by defects on the surface of the substrate 110 is further reduced.

In addition, since the refractive index of the protective film 130 adjacent to the substrate 110 is smaller than the refractive index of the first anti-reflection film 140 adjacent to the air, the reduction of the anti-reflection effect due to the refractive index of the protective film 130 is prevented. To do so, the thickness of the protective film 130 is preferably much smaller than the thickness of the first anti-reflection film 140.

As such, not only the anti-reflection effect of light using the refractive index changes of the protective layer 130 and the first anti-reflection layer 140 but also the electric field passivation effect by the fixed charge of the protective layer 130, and the protective layer 130 and the first anti-reflection layer By 140, a surface passivation effect is additionally obtained.

The front electrode 150 is positioned on the emitter part 120 and penetrates the protection part 130 and the first anti-reflection film 140 to be electrically and physically connected to the emitter part 120.

Although not specifically illustrated, the front electrode 150 may be formed in a grid pattern including a plurality of finger electrodes extending in one direction and a plurality of busbar electrodes extending in a direction intersecting the finger electrodes.

The front electrode 150 collects electric charges, for example holes, moved toward the emitter unit 120.

The front electrode 150 is at least selected from the group consisting of nickel (Ni), copper (Cu), tin (Sn), zinc (Zn), indium (In), titanium (Ti), gold (Au), and combinations thereof. It may be made of one conductive material.

The local rear electric field 160 is located locally on the rear surface of the substrate 110, and is electrically and physically connected to the rear electrode 170, and impurities of the same conductivity type as the substrate 110 are doped at a higher concentration than the substrate 110. Regions, for example, n+ or n++ regions.

Here, the fact that the local rear electric field 160 is locally located means that a certain distance is maintained between the local rear electric field 160, and each local rear electric field 160 is dot or line. It may be formed in a (line) pattern.

The local rear electric field 160 is formed by forming an impurity layer (see FIG. 2C, 1100) on the rear surface of the substrate 110 and then irradiating the impurity layer 1100 locally with a laser, in the first embodiment, The width W2 of the local rear electric field 160 is formed to be the same as the width W4 of the back electrode 170 (W2=W4), and the width W1 of the front electrode 150 to increase the light receiving area Is formed smaller than the width W4 of the back electrode 170.

The local rear electric field 160 forms a potential barrier due to a difference in the concentration of impurities with the substrate 110, thereby preventing hole movement toward the local rear electric field 160, which is an electron moving direction, while the local rear electric field 160 ( Electron movement toward 160) becomes easier. Therefore, the local back-side electric field 160 reduces the amount of charge lost due to the recombination of electrons and holes in and around the back surface of the substrate 110 and accelerates the movement of the desired charge (eg, electrons) to accelerate the back electrode 170 ) To increase the amount of charge transfer.

In addition, since the concentration of impurities in the local rear electric field 160 is higher than that of the substrate 110, the conductivity of the local rear electric field 160 is greater than that of the substrate 110. Therefore, the charge transfer from the local rear electric field 160 to the rear electrode 170 is more easily performed.

The insulating portion 162 is formed adjacent to both ends of the rear surface of the substrate 110, preferably the rear surface, and is spaced apart from the rear electrode 170 and the local rear electric field portion 160. At this time, the insulating portion 162 is formed of an insulating material such as a polymer (polymer).

The insulating portion 162 irradiates the laser to the impurity layer 1100 formed on the rear surface of the substrate 110 to form the local rear electric field portion 160, and irradiates the laser to the location where the insulating portion 162 is formed. It can be formed by.

Therefore, the insulating portion 162 is a high-concentration doping region 162A in which impurities of the same conductivity type as the substrate 110 are doped at a higher concentration than the substrate 110, for example, n+, like the local back-side electric field 160. Or n++ region.

In addition, the insulating portion 162 prevents the electrodes of different polarities formed on the front and rear surfaces of the substrate 110 from being electrically connected through the inversion layer 10 formed inside the rear surface and inside the side surface of the substrate 110. It further includes a depletion region (162B).

The depletion region 162B is formed at a junction portion between the inversion layer 10 having p-type conductivity and the high concentration doping region 162A having n-type conductivity, and the high concentration doping region 162A and the protective film 130 are formed. Located in between, it is formed to a thickness greater than or equal to the thickness of the inversion layer 10. Therefore, since the high concentration doped region 162A is electrically insulated from the inversion layer 10 by the depletion region 162B, charges collected from the rear surface of the substrate 110 are prevented from moving to the front surface of the substrate 110. .

The insulating portion 162 of this configuration is preferably formed close to the end of the rear surface of the substrate 110 in order to effectively suppress the increase in resistance and the recombination rate.

The depletion region 162B is formed with the same width W3 as the high concentration doped region 162A.

On the other hand, like the insulating portion 162, the local rear electric field portion 160 also includes a depletion region. However, the depletion region formed between the local rear electric field 160 and the protective layer 130 is removed in the process of forming the rear electrode 170. Thus, the back electrode 170 directly contacts the n+ or n++ region of the local back electric field 160.

In the first embodiment, the width W3 of the insulating portion 162 may be formed to be the same as the width W2 of the back electrode 170, or may be formed to be smaller than the width W2 of the back electrode 170.

As an example, the insulating portion 162 may be formed with a width W3 of 100 μm to 300 μm.

The second anti-reflection layer 142 is positioned only on the protective layer 130 located on the rear surface of the substrate 110 and is not located on the portion where the rear electrode 170 is located. The second anti-reflection film 142 is made of a material having a positive (+) fixed charge that prevents reflection of light and transmits light of the substrate 110. For example, it may be made of hydrogenated silicon nitride (SiNx:H), and may have a refractive index of 1.9 to 2.3 and a thickness of 50 nm to 100 nm.

In the first embodiment, the second anti-reflection film 142 is formed of the same material as the first anti-reflection film 140 and may have the same thickness as the first anti-reflection film 140.

However, when the solar cell is used as a single-sided light receiving type, the second anti-reflection film 142 may be omitted.

The rear electrode 170 penetrates the protection unit 130 and the second anti-reflection layer 142 and is electrically and physically connected to the local rear electric field unit 160. The back electrode 170 is formed at the same position as the local back electric field 160.

Accordingly, in FIG. 1, the left end and the right end of the rear electrode 170 coincide with the left end and the right end of the local rear electric field 160, respectively.

The back electrode 170 may be formed in a grid pattern including a finger electrode and a bus bar electrode, like the front electrode 150.

The back electrode 170 collects electric charges moving toward the substrate 110, for example, electrons, and outputs them to an external device. The back electrode 170 is aluminum (A), nickel (Ni), copper (Cu), silver (Ag), tin (Sn), zinc (Zn), indium (In), titanium (Ti), gold (Au) And it may be made of at least one conductive material selected from the group consisting of a combination thereof.

The operation of the solar cell according to the first embodiment having such a structure is as follows.

When light irradiated to the solar cell is incident into the interior of the substrate 110 through the emitter unit 120, electron-hole pairs are generated in the substrate 110 by the light energy incident on the substrate 110.

At this time, since the front surface of the substrate 110 is a texturing surface, light reflectivity at the front surface of the substrate 110 decreases, and incident and reflection operations are performed at the texturing surface to trap light inside the solar cell. Since the light absorption rate increases, the efficiency of the solar cell is improved.

In addition, the first passivation layer 130 and the first anti-reflection layer 140 located on the front surface of the substrate 110 and the first passivation layer 130 and the second anti-reflection layer 142 located on the back side of the substrate 110 By reducing the reflection loss of light incident on the substrate 110 by the amount of light incident on the substrate 110 is further increased.

These electron-hole pairs are separated from each other by a pn junction of the substrate 110 and the emitter portion 120, and the electrons move toward the substrate 110 having an n-type conductivity type, and the hole is a p-type conductivity type. It moves toward the emitter portion 120 having.

As such, electrons moved toward the substrate 110 move to the rear electrode 170 through the local rear electric field 160, and holes moved toward the emitter portion 120 move to the front electrode 150.

Therefore, when the front electrode 150 of any one solar cell and the rear electrode 170 of the adjacent solar cell are connected by a conductor or the like, an electric current flows, and this is used as power from the outside.

At this time, the insulating portion 162 located on the rear surface of the substrate 110 prevents charges collected from the rear surface of the substrate 110 from being transferred to the front surface of the substrate 110 through the inversion layer 10.

Hereinafter, a method of manufacturing a solar cell according to a first embodiment of the present invention will be described with reference to FIGS. 2A to 2I.

First, as shown in FIG. 2A, the entire surface of the n-type semiconductor substrate 110 containing n-type impurities is etched to form a textured surface that is an uneven surface.

In general, the substrate 110 made of a silicon wafer is manufactured by slicing a silicon block or ingot with a blade or a multi wire saw.

On the other hand, when slicing a silicon block or ingot, a mechanical damage layer is formed on the silicon wafer.

Therefore, in order to prevent the deterioration of the characteristics of the solar cell due to the mechanical damage layer, a wet etching process for removing the mechanical damage layer is performed. At this time, in the wet etching process, an alkali or acid etchant is used.

After removing the mechanical damage layer, the entire surface of the substrate 110 is formed as a textured surface by using a wet etching process or a dry etching process using plasma.

Next, as shown in FIG. 2B, a p-type emitter portion 120 is formed on the n-type semiconductor substrate 110. The emitter unit 120 may be formed on the substrate 110 by a lamination process such as, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD), but is not limited thereto. It may be formed by implanting or diffusing an impurity of a trivalent element on one surface of the substrate 110, for example, a textured surface using ion implantation or heat diffusion. At this time, the emitter part 120 has an uneven surface under the influence of the shape of the textured surface of the substrate 110.

Next, as illustrated in FIG. 2C, an impurity layer 1100 including impurities of a pentavalent element is formed on the other surface of the substrate 110, that is, the back surface. The impurity layer 1100 is formed by a method such as a direct printing method, a spray doping method, a spin temperature doping method, a paste coating method using a screen printing method, or the like.

Next, as shown in FIG. 2D, a partial region of the impurity layer 1100, in particular, a region where the back electrode 170 is to be located, and lasers are locally irradiated to both ends of the back side of the substrate 110, thereby generating a plurality of local back surfaces. The stepped portion 160 and the plurality of high-concentration doped regions 162A are simultaneously formed. At this time, the plurality of local rear electric field parts 160 are located locally on the rear surface of the substrate 110, and the plurality of high concentration doped regions 162A are formed adjacent to both ends of the rear surface of the substrate 110, and the plurality of local rear electric field parts are disposed. Located away from the step 160.

The plurality of local rear electric field parts 160 and the plurality of high-concentration doped regions 162A are regions in which impurities of the same conductivity type as the substrate 110 are doped at a higher concentration than the substrate 110, for example, n+ or n++ regions. It is formed identically to each other.

Next, as shown in FIG. 2E, the impurity layer 1100 is removed. At this time, the impurity layer 1100 may be removed by an etch method that does not affect the substrate 110 including the emitter portion 120, the plurality of local rear electric field portions 160, and the plurality of high concentration doping portions 162A. have. For example, the impurity layer 1100 may be removed through dry etching or wet etching.

Next, as shown in FIG. 2F, aluminum oxide (AlO _x ) is deposited on the entire surface of the substrate 110 to form a protective layer 130. That is, the passivation layer 130 is formed on the emitter portion 120, on the back side of the substrate 110, and on both sides of the substrate 110. The protective film 130 may be formed to have a refractive index of 1.55 to 1.7 and a thickness of 5 nm to 30 nm.

In this case, the protective layer 130 may be formed using atomic layer deposition (ALD). When the protective layer 130 is formed by using an atomic layer deposition method, the protective layer 130 may be formed not only on the front side but also on the back side and side of the substrate 110 in a single deposition process. Therefore, since the protective films 130 located on the front and rear surfaces of the substrate 110 are formed under the same process conditions, they have the same film characteristics.

However, aluminum oxide (AlO _x ) has a negative (-) fixed charge. Accordingly, when the protective layer 130 is formed, an inversion layer 10 charged with a positive charge is formed inside the back surface and inside the side surface of the substrate 110, and the inversion layer 10 and the high concentration doping portion 162A are formed. ) And a depletion region 162B are formed between the inversion layer 10 and the local rear electric field 160.

Specifically, the depletion region 162B formed between the inversion layer 10 and the high-concentration doping portion 162A includes the inversion layer 10 having a p-type conductivity and the high concentration doping region 162A having an n-type conductivity. It is formed at the junction portion, and is located between the high-concentration doped region 162A and the protective layer 130, and is formed to a thickness greater than or equal to the thickness of the inversion layer 10. Therefore, since the high concentration doped region 162A is electrically insulated from the inversion layer 10 by the depletion region 162B, charges collected from the rear surface of the substrate 110 are prevented from moving to the front surface of the substrate 110. .

On the other hand, the depletion region 162B formed between the inversion layer 10 and the local back field portion 160 has a p-type conductivity layer 10 and a n-type local back electric field portion 160 having conductivity. It is formed at the junction of ), located between the local rear electric field 160 and the protective film 130, and is formed to a thickness greater than or equal to the thickness of the inversion layer 10. Therefore, the local rear electric field 160 is electrically insulated from the inversion layer 10 by the depletion region 162B, so that charges collected from the rear surface of the substrate 110 are prevented from moving to the front surface of the substrate 110. do.

Next, as illustrated in FIG. 2G, hydrogenated silicon nitride (SiNx:H) is deposited on front and rear surfaces of the substrate 110 to form a first antireflection film 140 and a second antireflection film 142, respectively. .

At this time, the first anti-reflection film 140 is formed on the entire upper surface of the protective film 130, and the second anti-reflection film 142 is formed on the entire rear surface of the protective film 130.

In addition, the first anti-reflection film 140 and the second anti-reflection film 142 may be formed by a method such as plasma enhanced chemical vapor deposition (PECVD) or sputtering.

At this time, the first anti-reflection film 140 and the second anti-reflection film 142 may be formed to have a refractive index of 1.9 to 2.3 and a thickness of 50 nm to 100 nm. That is, the first anti-reflection film 140 and the second anti-reflection film 142 may be formed thicker than the protective film 130.

Subsequently, as illustrated in FIGS. 2H and 2I, the front electrode 150 is formed through the protective film 130 and the first anti-reflection film 140 and in contact with the emitter part 120 positioned below the protective film 130. 130) and a plurality of rear electrodes 170 that penetrate the second anti-reflection layer 142 and contact the plurality of local rear electric field units 160 positioned below the second anti-reflection layer 142.

The front electrode 150 and the back electrode 170 may be formed by printing, drying, and firing an electrode paste containing an etching component, or by using a plating process.

In the case of forming the front electrode 150 and the back electrode 170 using the electrode paste, the etching components included in the paste in the firing process may include the first and second anti-reflection films 140 and 142 and the protective film 130. It will be etched. Therefore, the front electrode 150 is electrically and physically connected to the emitter portion 120, and the back electrode 170 is electrically and physically connected to the local rear electric field portion 160.

Alternatively, in the case of using a plating process, openings exposing the emitter unit 120 and the local rear electric field unit 160 by removing portions of the protective layer 130 and the first and second antireflection layers 140 and 142, respectively After forming, the front electrode 150 and the back electrode 170 may be formed by plating the electrode material in the opening.

Meanwhile, since the back electrode 170 has the same width W4 as the local rear electric field 160 and is formed at the same position, the depletion region 162B formed in the local rear electric field 160 is removed.

However, since the back electrode 170 is not formed in the insulating portion 162, a depletion region 162B continues to exist between the high concentration doping portion 162A of the insulating portion 162 and the protective layer 130.

Therefore, the insulating portion 162 prevents charges collected from the rear surface of the substrate 110 from being transferred to the front surface of the substrate 110 through the inversion layer 10.

Hereinafter, a solar cell according to the second and third embodiments of the present invention will be described with reference to FIGS. 3 and 4.

Referring to FIGS. 3 and 4, the solar cells according to the second and third embodiments of the present invention have the same configuration as the solar cell of the first embodiment except for the local rear electric field 160 and the rear electrode 170. Since the same, hereinafter, only the local rear electric field 160 and the rear electrode 170 will be described. Therefore, components that perform the same function as the solar cell illustrated in FIG. 1 are denoted by the same reference numerals as in FIG. 1 and detailed description thereof is omitted.

In the solar cell according to the above-described first embodiment, forming the back electrode 170 at the same width as the local back electric field 160 may not be easy in the process.

Therefore, in the solar cell according to the second and third embodiments, the width W4 of the back electrode 170 is formed to be smaller than the width W2 of the local back electric field 160.

First, referring to FIG. 3, the solar cell according to the second embodiment is formed at a position corresponding to the local rear electric field 160, and the rear electrode 170 positioned at a central portion of the local rear electric field 160 It includes.

The local rear electric field 160 includes a contact region connected to the rear electrode 170 and first and second margin regions 24a and 24b excluding the contact region.

However, the first and second margin regions 24a and 24b are located in the p-n junction region, like the depletion region 162B of the insulating portion 162. Therefore, since the first and second margin regions 24a and 24b become depletion regions, a floating junction in which positive (+) charges of the inversion layer 10 rapidly falls to the rear electrode 170 is first. And the second margin regions 24a, 24b. Therefore, a parasitic shunt between the inversion layer 10 and the back electrode 170 is prevented. At this time, a leakage current between the inversion layer 10 and the back electrode 170 is generated to prevent a parasitic shunt, which may decrease the short-circuit current density Jsc, thereby preventing a decrease in efficiency of the solar cell.

Since the rear electrode 170 is formed corresponding to the position of the rear electric field 160, the width W21 of the contact area is formed to be the same as the width W4 of the rear electrode 170, and the first and second margins The widths W21a and W21b of the regions 24a and 24b are formed to be the same as each other.

Further, the width W21 of the contact area is formed equal to the width of the first and second margin areas 24a and 24b combined with the widths W21a and W21b, or the first and second margin areas 24a and 24b The widths W21a and W21b may be formed larger than the combined widths. The widths W21a + W21b of the second and third margin regions 24a and 24b may be 100 μm to 300 μm.

Next, referring to FIG. 4, the solar cell according to the third embodiment is formed at a position corresponding to the local rear electric field 160 and the rear electrode 170 positioned at one end of the local rear electric field 160 It includes.

The local rear electric field 160 includes a contact region connected to the rear electrode 170 and a third margin region 24c excluding the contact region. The third margin region 24c is formed as a depletion region like the first margin region 24a and the second margin region 24b, and by electrically blocking the floating junction, the inversion layer 10 and the back electrode 170 are formed. Prevents parasitic shunts of the family.

The width W21 of the contact region may be formed to be the same as the width W4 of the back electrode 170, and may be formed to be the same as the width W21 of the third margin region 22c. The width W21c of the third margin region 24c may be formed from 100 μm to 300 μm.

In addition, although not shown, the rear electrode 170 may be formed at a position different from the embodiment illustrated in FIGS. 3 and 4 in an area overlapping the local rear electric field 160.

Although the 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 concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

110: substrate 120: emitter portion
130: protective film 140: the first anti-reflection film
142: second anti-reflection film 150: front electrode
160: local rear electric field 162: insulation
170: rear electrode

Claims (13)

A substrate having a first conductivity type;
An emitter portion located on the front surface of the substrate and having a second conductivity type opposite to the first conductivity type;
A first electrode electrically connected to the emitter portion;
A plurality of local backside electric field portions located locally on the back side of the substrate and containing impurities of the first conductivity type in a higher concentration than the substrate;
A second electrode electrically connected to the plurality of local rear electric fields;
A protective film formed on a front surface, a rear surface, and both side surfaces of the substrate in a region where the first electrode and the second electrode are not located, and formed of a material having a fixed charge having the same polarity as the first conductive type;
An inversion layer located in some regions of the rear surface of the substrate and both side surfaces of the substrate and having the second conductivity type; And
A plurality of insulating parts formed in a region where the inversion layer is not located in the inside of the rear surface of the substrate to electrically insulate the emitter part and the plurality of local back electric field parts.
Including,
The plurality of insulating portions are located between the high-concentration doping portion and the high-concentration doping portion and the passivation layer, which contain the first conductivity type impurities at a higher concentration than the substrate, and the emitter portion and the plurality of local regions through the reverse layer. A solar cell including a depletion region blocking electrical connection between a rear electric field portion and the emitter portion and the high concentration doping portion. delete In claim 1,
The second electrode is located in a region overlapping the local rear electric field. In claim 3,
The width of the second electrode is formed smaller than the width of the local rear electric field. In claim 4,
The plurality of local rear electric field units,
A contact area in contact with the second electrode; And
A solar cell including a margin region excluding the contact region. In claim 5,
The margin region is a solar cell formed of a depletion region. In claim 5,
The width of the contact area and the width of the margin area are the same as the solar cell. In any one of claims 1 and 3 to 7,
The protective layer is a solar cell including aluminum oxide (AlO _x ) having a negative fixed charge. In claim 8,
A solar cell further comprising an anti-reflection film positioned on the protective film. In claim 9,
The anti-reflection film is a solar cell formed of silicon nitride having a positive (+) fixed charge. Forming an emitter portion having a second conductivity type opposite to the first conductivity type on a front surface of a substrate having a first conductivity type;
Forming a plurality of local back surface electric fields and a plurality of insulating parts on the back surface of the substrate;
Forming protective films on front, rear, and both sides of the substrate; And
Forming a front electrode positioned on the front surface of the substrate and connected to the emitter unit, and a rear electrode positioned on the rear surface of the substrate and connected to the plurality of local rear electric field units
Including,
The plurality of insulating portions are located between the high-concentration doping portion and the high-concentration doping portion and the passivation layer, which contain impurities of the first conductivity type at a higher concentration than the substrate, and the protective film is disposed inside and behind the rear surface of the substrate A method of manufacturing a solar cell including a depletion region blocking electrical connection between the emitter portion, the plurality of local rear electric field portions, and the emitter portion and the high-concentration doping portion through an inversion layer formed. In claim 11,
The forming of the plurality of local rear electric fields and the plurality of insulating parts may include:
Forming an impurity layer on the rear surface of the substrate; And
Locally irradiating the impurity layer with a laser
The method of manufacturing a solar cell formed according to. In claim 12,
The protective film is a method of manufacturing a solar cell formed on the entire surface of the substrate using atomic layer deposition (atomic layer deposition, ALD) method.

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