KR101276888B1 - Solar cell - Google Patents

Abstract

The present invention relates to a solar cell. The solar cell includes a substrate made of a crystalline semiconductor, an emitter portion formed of an amorphous semiconductor and forming a pn junction with the substrate, a first protection portion formed on the substrate and made of an oxide, a first electrode connected to the emitter portion, And a second electrode electrically connected to the substrate. As a result, the passivation function is performed by a film made of an oxide having excellent film quality and uniformity in the portion in contact with the surface of the substrate. Thus, the passivation function is improved and the efficiency of the solar cell is improved.

Description

  Solar cell {SOLAR CELL}

The present invention relates to a solar cell.

With the recent prediction of the depletion of existing energy sources such as petroleum and coal, there is a growing interest in alternative energy to replace them, and thus solar cells producing 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, electron holes are generated in the semiconductor, and electrons and holes generated by the p-n junction move toward the n-type semiconductor portion and the p-type semiconductor portion, respectively. The moved electrons and holes are collected by different electrodes connected to the n-type semiconductor portion and the p-type semiconductor portion, respectively, and connected to the wires to obtain electric power.

The technical problem to be achieved by the present invention is to improve the efficiency of the solar cell.

A solar cell according to an aspect of the present invention comprises a substrate made of a crystalline semiconductor, an amorphous semiconductor, an emitter portion forming a pn junction with the substrate, a first protection portion formed on the substrate and consisting of an oxide, the emitter portion And a first electrode connected to the substrate, and a second electrode electrically connected to the substrate.

An impurity of the same conductivity type as the substrate may be further disposed on the first protective part, and may further include an electric field part formed of an amorphous semiconductor.

The first protective part may have a thickness of 1 nm to 10 nm.

The first protection part may have a fixed charge.

The first protection part may be positioned on an incident surface of the substrate, and the first protection part may have a fixed charge having a polarity opposite to the conductivity type of the substrate.

The fixed charge of the first protective part may be 1 × 10 ¹² / cm 2 to 1 × 10 ¹⁵ / cm 2.

When the substrate has a p-type conductivity type, the first protection part may be made of aluminum oxide, and when the substrate has an n-type conductivity type, the first protection part may be made of silicon oxide.

The first protective part may have a thickness of 3 nm to 20 nm.

The solar cell according to the above features may further include an electric field part disposed on the first protective part and containing an impurity of the same conductivity type as that of the substrate and higher than the substrate, and comprising an amorphous semiconductor.

The first protective part may be made of silicon oxide, aluminum oxide, or zinc oxide.

The emitter portion may be positioned on a surface of the substrate positioned opposite to the incident surface of the substrate.

The solar cell according to the above features may further include an electric field portion formed on an amorphous semiconductor, spaced apart from the emitter portion on the surface of the substrate on which the emitter portion is located, and containing impurities of the same conductivity type as that of the substrate. .

The solar cell according to the above feature may further include a second protection part having a first protection part located between the substrate and the emitter part and a second protection part located between the substrate and the electric field part.

The first protective portion and the second protective portion may each have a thickness of 1 nm to 10 nm.

The first protective portion and the second protective portion may each have a fixed charge.

Polarities of the fixed charges of the first protective part and the second protective part may be opposite to each other.

The first protective portion may have a fixed charge of the same polarity as the conductive type of the substrate, and the second protective portion may have a fixed charge of the polarity opposite to the conductive type of the substrate.

The first protective portion and the second protective portion may each have a fixed charge of 1 × 10 ¹² / cm 2 to 1 × 10 ¹⁵ / cm 2.

The first protective portion and the second protective portion may each have a thickness of 3 nm to 20 nm.

The emitter unit may be positioned on an incident surface of the substrate to which light is incident.

The first protection part may be located between the emitter part and the substrate.

The first protective part may have a fixed charge having a polarity opposite to that of the conductive type of the substrate.

The display device may further include a second protection part formed of an oxide on the surface of the substrate positioned opposite to the incident surface.

The second protective part may be made of silicon oxide, aluminum oxide, or zinc oxide.

The electronic device may further include an electric field part disposed on the second protection part and formed of an amorphous semiconductor, and the second electrode may be electrically connected to the substrate through the electric field part.

The second protective part may have a fixed charge having a polarity opposite to that of the conductive type of the substrate.

The solar cell according to the above feature may further include an electric field part formed of an amorphous semiconductor on the second protection part, and the second electrode may be electrically connected to the substrate through the electric field part.

As a result, the passivation function is performed by a film made of an oxide having excellent film quality and uniformity in the portion in contact with the surface of the substrate, so that the passivation function is improved and the efficiency of the solar cell is improved. In addition, since the passivation function due to the fixed charge of the oxide is further performed, the efficiency of the solar cell is further improved.

1 and 2 are some cross-sectional views of examples of solar cells according to one embodiment of the invention, respectively.
3 and 4 are partial cross-sectional views of examples of solar cells according to another embodiment of the present invention, respectively.
5 and 6 are partial cross-sectional views of solar cells according to still 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 order to clearly illustrate the present invention in the drawings, portions not related to the description are omitted, and like reference numerals are given to similar portions 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.

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

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

The solar cell 11 illustrated in FIG. 1 includes a front protection part 191 positioned on a substrate 110 and an incident surface (hereinafter, referred to as a “front surface”), which is a surface of the substrate 110 on which light is incident. , A front surface field (FSF) 171 positioned on the front protective portion 191, an antireflection portion 130 positioned on the front electric field portion 171, and a substrate 110 that is opposite to the incident surface. A plurality of emitter parts 121 located on a surface (hereinafter referred to as a 'rear surface') side, and a plurality of rear electric field parts located on a rear side of the substrate 110 and spaced apart from the plurality of emitter parts 121. 142, a plurality of first electrodes 141 respectively positioned on the plurality of emitter units 121, and a plurality of second electrodes each disposed on the plurality of back surface fields BSF 172 ( 142).

The substrate 110 is a semiconductor substrate made of silicon of a first conductivity type, for example, an n-type conductivity type. At this time, the silicon is crystalline silicon such as monocrystalline silicon or polycrystalline silicon. When the substrate 110 has an n-type conductivity type, impurities of pentavalent elements, such as phosphorus (P), arsenic (As), and antimony (Sb), are doped to 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.

The substrate 110 may be a damage damage removal process performed on a flat surface of the substrate 110 or a texturing process performed on a surface of the substrate 110 after a flat surface or damage layer removal process of the substrate 110 is performed. Has an uneven surface. That is, when the substrate 110 is made of polycrystalline silicon, a damage layer removing process may be performed, and when the substrate 110 is made of single crystal silicon, a texturing process may be performed to form an uneven surface.

The substrate 110 may have an uneven surface on the rear surface as well as the front surface.

The front protective part 191 located on the front surface of the substrate 110 converts defects such as dangling bonds, which are mainly present on and near the surface of the substrate 110, into stable bonds, thereby causing the substrate to be damaged by the defect. A passivation function is performed to reduce the dissipation of charge that has migrated toward the surface of 110, thereby reducing the amount of charge lost at or near the surface of the substrate 110 by the defect.

The front protection part 191 is formed of an oxide such as silicon oxide (SiOx), aluminum oxide (eg, Al ₂ O ₃ ), zinc oxide (eg, ZnO), or the like.

The oxide used as the front protective part 191 may be formed by chemical vapor deposition (CVD) or plasma enhanced vapor deposition (PECVD).

When the front protection part 191 is formed of silicon oxide (SiOx), the front protection part 191 is made of silicon dioxide (SiO ₂ ) formed by a thermal oxidation method.

In general, when the silicon dioxide film (SiO ₂ ) is formed by the thermal oxidation method, the uniformity of the silicon dioxide film (SiO ₂ ) formed on the substrate 110 is increased and the film quality and the step difference are applied, compared to the silicon oxide film formed by other processes. Excellent step coverage.

In addition, since the formation thickness of the silicon dioxide film (SiO ₂₎ is formed according to the process time and process temperature variable, it is possible to form the process time and process, silicon dioxide film (SiO ₂₎ of easily a desired thickness by adjusting the temperature .

In addition, when the front protection part 191 is formed using aluminum oxide and zinc oxide, aluminum oxide and zinc oxide are formed by atomic layer deposition (ALD).

Unlike chemical vapor deposition or physical vapor deposition, which injects various reactants into the process chamber at the same time to grow the film, atomic layer deposition separates each reactant (precursor) and supplies them to the process chamber separately. It is a technique using the chemical adsorption and desorption reaction of the monoatomic layer by the surface saturation reaction of the reactant. The atomic layer deposition method includes a process of discharging gases that are not adsorbed to the surface of the substrate, in which each reaction gas (material) is alternately supplied into the reaction chamber. In addition, since each of the reactants is saturated with a monolayer on the surface of the substrate, the thin film formed by the self limiting reaction has excellent step coverage and can be controlled precisely by controlling the number of steps. Thin film formation is also possible.

Therefore, when the front surface protection unit 191 is formed by growing silicon dioxide (SiO ₂ ), aluminum oxide, or zinc oxide by thermal oxidation or atomic layer deposition, it is formed on the substrate 110 in comparison with other film forming processes. The uniformity of the film is improved and the film quality is excellent, so that the passivation function is further improved. In addition, since the atomic layer deposition method is performed at a lower temperature (about 500 degrees or less) than the chemical vapor deposition method, the deterioration phenomenon of the substrate 110 is also reduced.

In the solar cell of the comparative example, the front protective portion is made of amorphous silicon (a-Si).

However, since amorphous silicon has a high resistance value, in order to reduce the series resistance of the solar cell, the amorphous silicon film is formed to a very thin thickness such as about 2 nm to 3 nm. Therefore, it is difficult to uniformly form amorphous silicon regardless of the position on the surface of the substrate. That is, the amorphous silicon film has a low uniformity. In particular, when the surface of the substrate is uneven and the uneven surface on which the unevenness is formed, the uniformity of the amorphous silicon film is further reduced. Therefore, there is a portion where the amorphous silicon film is not formed on the surface of the substrate, which causes a problem that the passivation function is not performed in the portion where the amorphous silicon film is not located, thereby greatly reducing the passivation effect.

In addition, the crystallization phenomenon of the amorphous silicon film easily proceeds at a temperature of about 200 ° C. or more, and the passivation function is greatly degraded due to the crystallization phenomenon of the amorphous silicon film.

As already explained. Since the thickness of the amorphous silicon film formed on the substrate by the high resistance value is very thin, it is necessary to form the amorphous silicon film in a very short time. Therefore, it is very difficult to stably and uniformly grow a very thin film of about 2 nm to 3 nm on a substrate using chemical vapor deposition or plasma chemical vapor deposition, resulting in low reproducibility of the process.

However, as described above, when the front protection portion 191 is formed of an oxide, since the uniformity and film quality of the oxide are improved and the reactivity of the oxide is greater than that of the amorphous silicon, the passivation effect is greatly improved, thereby improving the efficiency of the solar cell 11. do.

In addition, since the crystallization of the oxide is not easily performed at a high temperature as compared with the amorphous silicon film, the film characteristics of the front protective part 191 made of the oxide do not change, and the passivation effect due to the crystallization phenomenon does not decrease.

Furthermore, when the front protection part 191 is formed by the thermal oxidation method and the atomic layer deposition method, since the thickness of the front protection part 191 is easily controlled, a thin front sign part 191 having a thickness of several nm or less may be used. Formation is also very easy and accurate, the manufacturing process of the solar cell 11 becomes easy, and the process is excellent in reproducibility.

In this example, the thickness of the front protective part 191 made of oxide may have a thickness of about 1 nm to 10 nm.

When the front protection part 191 has a thickness of about 1 nm or more, the uniformity of the front protection part 191 formed on the substrate 110 may be increased to perform a more stable passivation function, and the front protection part 191 ) Has a thickness of about 10 nm or less, the amount of light absorbed in the front protective part 191 may be further reduced to further increase the amount of light incident into the substrate 110.

The front electric field part 171 positioned on the front protection part 191 is an impurity part in which impurities of the same conductivity type (eg, n-type) as the substrate 110 are contained at a higher concentration than the substrate 110.

The front electric field unit 171 of the present embodiment may be made of amorphous silicon.

Due to the impurity concentration difference between the substrate 110 and the front surface electric field unit 171, a potential barrier is formed to perform a front surface electric field function that prevents charge (eg, hole) movement toward the front surface of the substrate 110. Therefore, the front field effect that the holes moving toward the front surface of the substrate 110 is returned to the rear surface of the substrate 110 by the potential barrier is obtained, thereby increasing the output amount of the electric charge output to the external device and The amount of charge lost by recombination or defects at the front of 110 is reduced.

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 may be formed of a silicon nitride film (SiNx) or a silicon oxide film (SiOx).

In addition, the anti-reflection unit 130 may include indium tin oxide (ITO), tin oxide (eg SnO 2), zinc oxide (eg ZnO, ZnO: Al, ZnO: B, AZO), and mixtures thereof. It may be formed of a transparent metal oxide formed at least one selected from the group consisting of.

Such metal oxides have better transparency than silicon nitride or silicon oxide. Therefore, when the anti-reflection portion 130 is made of a transparent metal oxide, the amount of light incident into the substrate 110 is further increased to further improve the efficiency of the solar cell 11.

In the present embodiment, the anti-reflection unit 130 may have a single layer structure but may have a multilayered layer structure such as a double layer, and may be omitted as necessary.

The plurality of emitter units 121 are spaced apart from each other in the rear surface of the substrate 110 and extend in parallel to each other.

The plurality of emitter portions 121 are regions formed by doping the second conductive type, for example, p-type impurities in the substrate 110, which are opposite to the conductive type of the substrate 110, and are connected to the substrate 110 and pn. To form.

Due to the built-in potential difference due to the pn junction formed between the substrate 110 and the plurality of emitter portions 121, electrons and holes, which are charges generated by light incident on the substrate 110, are each n. The hole moves toward the die and the hole moves toward the p die. Accordingly, when the substrate 110 is n-type and the emitter portion 121 is p-type, electrons move toward the rear surface of the substrate 110 and holes move toward the plurality of emitter portions 121.

 Since the emitter portion 121 forms a p-n junction with the substrate 110, unlike the present example, when the substrate 110 has a p-type conductivity type, the emitter portion 121 has an n-type conductivity type. In this case, holes move toward the rear surface of the substrate 110 and electrons move toward the emitter portion 121.

When the emitter portion 121 has a p-type conductivity type, impurities of a trivalent element may be doped in the rear surface of the substrate 110. On the contrary, when the emitter portion 121 has an n-type conductivity type. The impurities of the pentavalent element may be doped in the rear surface of the substrate 110.

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

The plurality of rear electric field parts 172 are spaced apart from the plurality of emitter parts 121 at the rear surface of the substrate 110, and are spaced apart from each other and extend in parallel with the plurality of emitter parts 121.

As shown in FIG. 1, the emitter unit 121 and the rear electric field unit 172 are alternately positioned within the substrate 110.

The rear electric field 172 is similar to the front electric field 171, and the rear electric field 172 which is a moving direction of electrons by a potential barrier due to a difference in impurity concentration between the substrate 110 and the rear electric field 172. While hindering hole movement toward C), it facilitates charge (eg, electron) movement toward back field 172. Accordingly, the amount of charge lost due to the recombination of electrons and holes in and around the backside electric field 172 is accelerated and the electron movement is accelerated to increase the amount of electron movement to the backside electric field 172.

As shown in FIG. 1, the width of each emitter portion 121 is different from the width of each rear electric field portion 171. For example, the width of the emitter portion 121 is greater than the width of the rear electric field portion 171. Big. However, in an alternative example, each emitter portion 121 and each backside field portion 171 may have the same width, or the width of each backside field portion 172 may be greater than the width of each emitter portion 121.

When the width of the emitter portion 121 is larger than the width of the rear electric field portion 172, the p-n junction region is increased, so that the generation amount of electron holes is increased, which is advantageous for collecting holes having low mobility compared to electrons.

On the other hand, when the width of the rear electric field unit 172 is larger than the width of the emitter unit 121, the rear electric field region exhibiting the rear electric field effect increases, so that the rear electric field effect due to the rear electric field unit 172 increases. .

The plurality of first electrodes 141 positioned on the plurality of emitter portions 121 extend along the plurality of emitter portions 121 and are electrically and physically connected to the plurality of emitter portions 121.

Each first electrode 141 collects electric charges, for example, holes moved toward the corresponding emitter part 121.

The plurality of second electrodes 142 positioned on the plurality of rear electric field parts 172 extend along the plurality of rear electric field parts 172, and are electrically and physically connected to the plurality of rear electric field parts 172. have.

Each second electrode 142 collects charge, for example, electrons, which move toward the corresponding backside field portion 172.

In FIG. 1, each of the first and second electrodes 141 and 142 may have the same planar shape as the emitter part 121 and the rear electric field part 172 positioned below, but may have different planar shapes. As the contact area between the emitter portion 121 and the rear electric field portion 172 and the first and second electrodes 141 and 142 increases, the contact resistance decreases, so that the charge transfer efficiency to the electrodes 141 and 142 increases. . On the other hand, when the planar shape of the plurality of first and second electrodes 141 and 142 is smaller than the planar shape of the emitter part 121 and the rear electric field part 172 positioned below, the plurality of first and second electrodes The manufacturing cost for forming the electrodes 141 and 142 is reduced, thereby facilitating the manufacturing process.

The first and second electrodes 141 and 142 may include nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin (Sn), zinc (Zn), indium (In), and titanium. It may be made of at least one conductive metal material selected from the group consisting of (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials other than the above. As such, since the plurality of first and second electrodes 141 and 142 are made of a metal material, the plurality of first and second electrodes 141 and 142 may transmit light passing through the substrate 110 toward the substrate 110. Reflect.

In the solar cell 11 according to the present exemplary embodiment having the structure as described above, the plurality of first electrodes 141 and the plurality of second electrodes 142 are positioned on the rear surface of the substrate 110 to which light is not incident. The operation 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 protection unit 191, and then enters the substrate 110, the substrate 110 is exposed to light energy. ) Electrons and holes are generated. At this time, since the surface of the substrate 110 has a concave-convex surface, the light reflectivity on the entire surface of the substrate 110 is reduced, and the efficiency of the solar cell 11 is improved. 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 the pn junction of the substrate 110 and the emitter portion 121, holes move toward the emitter portion 121 having a p-type conductivity type and electrons move toward the rear electric field portion 172 having an n-type conductivity type. The moved holes and electrons are transferred to the first electrode 141 and the second electrode 142, respectively, and collected by the first and second electrodes 141 and 142. When the first electrode 141 and the second electrode 142 are connected with a conductive wire, a current flows, which is used as power from the outside.

In this case, since the front protective part 191 is formed of an oxide such as silicon oxide (SiOx), aluminum oxide (Al ₂ O ₃ ), or zinc oxide (ZnO), which has excellent film quality and good film uniformity, the passivation effect is further increased. This improves the efficiency of the solar cell 11.

Next, another example according to an embodiment of the present invention is shown with reference to FIG. 2.

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

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 is the same as the solar cell 11 shown in FIG. 1 except that the front electric field is not located on the incident surface of the substrate 110.

Therefore, in the solar cell 12 according to the present example, the front protection part 191a and the antireflection part 130 are continuously positioned on the front surface of the substrate 110.

The front protection part 191a including the oxide film may have a fixed charge (QF) of positive polarity (+) or negative polarity (−) according to the type of the oxide film.

For example, when the substrate 110 has an n-type conductivity type, the front protective part 191a has a positive fixed charge QF, and the substrate 110 has a p-type conductivity type. In this case, the front protection part 191a has a negative fixed charge QF. In this case, the intensity of the fixed charge QF of the front protective part 191a has a stronger negative (+) or positive (+) polarity than the substrate 110. For example, one example of a material having a positive fixed charge may be silicon oxide (SiOx), and one example of a material having a negative fixed charge may be aluminum oxide (Al ₂ O ₃ ).

Thus, when the substrate 110 is n-type, the fixed charge of the front protective part 191a has the same polarity as the positive polarity of the holes, which are the minority carriers of the substrate 110, and thus the front surface of the substrate 110. The hole moving toward the side is pushed toward the rear side of the substrate 110 by the fixed charge of the front protective part 191a. In addition, when the substrate 110 is p-type, the fixed charge of the front protective portion 191a has a negative polarity, which is the same polarity as that of electrons which are minority carriers of the substrate 110, and thus toward the front surface of the substrate 110. The moving electrons are pushed toward the rear surface of the substrate 110 by the fixed charge of the front protection part 191a.

Therefore, since the desired charge is transferred to the rear surface of the substrate 110 where the first or second electrodes 141 and 142 which output electrons or holes are moved, the electrons output to the first or second electrodes 141 and 142. I increase the amount of holes.

As such, the larger the size of the fixed charge QF is, the more advantageous it is to obtain a charge transfer control effect using the fixed charge of the front protective part 191a. For example, the size of the fixed charge QF may be about 1 × 10 ¹² / cm 2 to 1 × 10 ¹⁵ / cm 2. At this time, the size of the fixed charge QF can be controlled by adjusting the composition ratio of the oxide.

When the size of the fixed charge is about 1 × 10 ¹² / cm 2 or more, it is possible to more advantageously control the movement of the charge using the fixed charge of the front protective part 191a, and the size of the fixed charge is about 1 × 10 ¹⁵ / cm 2. In the following case, the front protection part 191a may be more easily formed without changing the physical characteristics of the front protection part 191a.

Therefore, the front protective part 191a has a function of preventing the movement of the desired charge toward the front surface of the substrate 110 by using the polarization of the fixed charge as well as the passivation function described above with reference to FIG. 1. 191a has a function similar to that of the front electric field unit 171 shown in FIG. 1. Since the solar cell 12 according to the present example does not need to have a separate front electric field unit 171, the manufacturing time and the manufacturing cost of the solar cell 12 are further reduced.

At this time, since the front protection unit 191a should have a fixed charge of a size that can interfere with the movement of the desired charge, the front protection unit 191a according to the present example is the front protection unit 191 of FIG. It may have a thickness thicker than the thickness, for example, the thickness of the front protective portion 191a may have a thickness of about 3nm to 20nm.

When the thickness of the front protective part 191a is about 3 nm or more, the uniformity of the front protective part 191a is further increased to form a fixed charge of a desired size formed on the substrate 110, thereby providing a more stable passivation function. When the front protective part 191a has a thickness of about 20 nm or less, the amount of light incident into the substrate 110 is further reduced by reducing the amount of light absorbed in the front protective part 191. Can be increased further.

In addition, since the front protective portion 191a of the solar cell 12 shown in FIG. 2 is formed of an oxide film, as described above with reference to FIG. 1, the uniformity and film quality of the film are improved and a crystallized shape is generated at a high temperature. By doing so, the passivation effect is greatly improved, and the thickness control of the front protective part 191a is easily performed.

As shown in FIG. 2, even when the front protection 191a of the solar cell 12 controls the movement of the desired charge using the fixed charge QF, in an alternative example, the solar cell 12 is shown in FIG. 1. An additional front electric field unit such as the illustrated front electric field unit 171 may be further provided. In this case, the front electric field unit 171 is positioned between the front protective unit 191a and the antireflection unit 130 as in the case of FIG. 1. In this case, since the front passivation function by the front electric field unit 171 is additionally performed, further preventing the transfer of unwanted charges to the front of the substrate 110, the amount of charge loss is reduced, and the first or second electrodes are reduced. The amount of charge output to 141 and 142 is increased.

Next, the solar cells 13 and 14 according to another embodiment of the present invention will be described with reference to FIGS. 3 and 4.

In comparison with FIGS. 1 and 2, the same reference numerals are used to designate components having the same function, and detailed description thereof will be omitted.

Unlike the solar cells 11 and 12 illustrated in FIGS. 1 and 2, the solar cells 13 and 14 illustrated in FIGS. 3 and 4 have a plurality of emitter portions 121a and a plurality of emitter portions 121a disposed on the substrate 110. The rear electric field part 172a forms a hetero junction with the substrate 110. Thus, in the solar cells 13 and 14 shown in FIGS. 3 and 4, the substrate 110 is made of a crystalline semiconductor such as polycrystalline or polycrystalline silicon, whereas the plurality of emitter portions 121a and the plurality of rear electric field portions are provided. Reference numeral 172a is made of an amorphous semiconductor such as amorphous silicon.

First, the heterojunction solar cell 13 shown in FIG. 3 is demonstrated.

The solar cell 13 shown in FIG. 3 has a structure similar to that of the solar cell 11 shown in FIG.

That is, as described above, the solar cell 13 includes a substrate 110 made of crystalline semiconductor, a front protective part 191 sequentially positioned on the front surface of the substrate 110, a front electric field part 171, and an anti-reflection part 130. The plurality of emitter portions 121a positioned on the rear surface of the substrate 110 and extending in parallel to each other, are spaced apart from the plurality of emitter portions 121a on the rear surface of the substrate 110 and parallel to each other. A plurality of rear electric field parts 172a extending along the plurality of first electrodes 141 positioned on the plurality of emitter parts 121a and a plurality of second electrodes 142 positioned on the plurality of rear electric field parts 172a. ).

At this time, unlike FIG. 1, the plurality of emitter portions 121a of the solar cell 13 are formed on the rear surface of the substrate 110 through PECVD or the like, and are formed of an amorphous semiconductor such as amorphous silicon. As shown in FIG. 1, the plurality of emitter portions 121a contain impurities having different conductivity types from those of the substrate 110, and the substrate 110 and the plurality of emitter portions 120a form a p-n junction.

In addition, unlike the FIG. 1, the plurality of backside electric fields 172a are formed on the backside of the substrate 110 through PECVD or the like, and are formed of an amorphous semiconductor such as amorphous silicon. As shown in FIG. 1, the plurality of backside electric fields 172a contain impurities having the same conductivity type as that of the substrate 110 at a higher concentration than the substrate 110.

Accordingly, the rear electric field unit 172a performs a rear electric field function by forming a potential barrier due to a difference in impurity concentration with the substrate 110, similarly to the rear electric field unit 172 of FIG. 1. 172a reduces the amount of charge lost due to the recombination of electrons and holes in the backside and the vicinity of the substrate 110 and accelerates the movement of the desired charge (eg, holes) to improve the amount of charge transfer to the second electrode 142. Increase.

As described above with reference to FIG. 1, the front protection part 191 disposed on the front surface of the substrate 110 may include an oxide such as silicon oxide (SiOx), aluminum oxide (Al ₂ O ₃ ), or zinc oxide (ZnO). Consists of

Unlike the solar cell 11 shown in FIG. 1, the solar cell 13 according to the present example has a plurality of first rear protective parts 921 positioned on the rear surface of the substrate 110 and between the plurality of emitter portions 121a. And a rear protection portion 192 having a plurality of second rear protection portions 922 positioned between the rear surface of the substrate 110 and the plurality of rear electric field portions 172a.

In this case, the plurality of first rear protective parts 921 and the plurality of second rear protective parts 922 are the same as the front protective part 191, such as silicon oxide (SiOx), aluminum oxide (Al ₂ O ₃ ), or zinc oxide. It consists of an oxide such as (ZnO).

In this case, the oxide may be formed by chemical vapor deposition or plasma chemical vapor deposition. In particular, silicon oxide may be formed by a thermal oxidation method, and aluminum oxide or zinc oxide may also be formed by atomic layer deposition.

The back protection part 192 performs a passivation function similarly to the front protection part 191 described above to reduce the amount of electric charge lost by defects mainly existing on and near the surface of the substrate 110.

Each of the first rear protective portion 921 and the second rear protective portion 922 of the rear protective portion 192 may have a thickness of about 1 nm to 10 nm, similarly to the front protective portion 191. At this time, the thicknesses of the first rear protective portion 921 and the second rear protective portion 922 do not prevent charge transfer to the emitter portion 121a and the rear electric field portion 172a respectively positioned thereon.

When each of the first rear protective portion 921 and the second rear protective portion 922 has a thickness of about 1 nm or more, the first rear protective portion 921 and the second rear protective portion 922 formed on the substrate 110. ) Uniformity of the () may be further increased to perform the passivation function more stably, and when the first rear protective portion 921 and the second rear protective portion 922 each have a thickness of about 10 nm or less, the emitter portion ( The substrate 110 may be further reduced by reducing the amount of light absorbed in the first rear protective portion 921 and the second rear protective portion 922 without interrupting charge transfer to the rear electric field portion 172a 121a). It can further increase the amount of light incident into it.

Compared with FIG. 1, the solar cell 13 has an open voltage Voc due to heterojunction between amorphous silicon 121a and 172a having a large energy band gap (Eg) and the silicon substrate 110. do. Therefore, the efficiency of the solar cell 13 is further improved.

In addition, since the rear protection unit 192 is located not only on the front surface of the substrate 110 but also on the rear surface of the substrate 110, the amount of charge loss due to defects occurring in the front and rear surfaces of the substrate 110 and near them is greatly reduced. The efficiency of the battery 13 is further improved.

In addition, as described above with reference to the front protective portion 191, compared with the solar cell of the comparative example having a rear protective portion made of amorphous silicon, the film uniformity and film quality of the rear protective portion 192 is improved and at a high temperature. Since no crystallization phenomenon occurs, the passivation effect is greatly improved, and thickness control of the rear protective part 192 is easily performed.

The solar cell 14 shown in FIG. 4 does not include the front electric field unit 171 in the solar cell 13 shown in FIG. 3, but instead has the same front surface as the front protection unit 191a described with reference to FIG. 2. The protection part 191a is provided. Therefore, as described above with reference to FIG. 2, the front protective part 191a made of oxide and performing a passivation function has a fixed charge [eg, having a polarity opposite to that of the conductive type (eg, n-type) of the substrate 110. Positive polarity], thereby preventing the transfer of a desired kind of charge toward the front surface of the substrate 110 using a fixed charge.

For this reason, as described above, since the front electric field unit 171 can be omitted, the manufacturing time and manufacturing cost of the solar cell 14 are improved, and due to the fixed charge, the loss or recombination rate of the charge is reduced and the solar cell ( The efficiency of 14) is further improved.

However, as described above with reference to FIG. 2, even when the front protection part 191a having the fixed charge of the desired polarity is provided, the front electric field part (1) between the front protection part 191a and the anti-reflection part 130 may be provided. 171 may be located, in which case the front field effect can be obtained more efficiently.

In addition, a rear protective part having first and second rear protective parts 92a1 and 92a2 positioned below the plurality of emitter parts 121a and the plurality of rear electric field parts 172a on the rear surface of the substrate 110. 192a, like the front protection part 191a, is made of an oxide and has a fixed fixed charge.

For example, when the substrate 110 is of the n-type conductivity type, each of the plurality of first backside protection portions 92a1 positioned below the plurality of emitter portions 121a of the p-type conductivity type has a negative polarity, respectively. The plurality of second backside protection portions 92a2 having a fixed charge of, and positioned under the backside electric field portion 172a having an n-type conductivity type, each have a fixed charge of positive polarity.

Accordingly, electrons of negative polarity moving toward the emitter portion 121a by the first rear protective portion 92a1 of the negative polarity (−) are pushed toward the substrate 110, but holes having positive polarities are emitted to the emitter portion 121a. The amount of holes pulled toward the first electrode 141 increases, the recombination rate of electrons and holes in the emitter portion 121a decreases, and the amount of holes moving to the first electrode 141 increases.

Also, similar to the first backside protection portion 92a1, holes moved toward the backside field portion 172a by the second backside protection portion 92a2 of positive polarity (+) are electrons instead of being pushed toward the substrate 110. Is pulled toward the rear electric field 172a, so that the recombination rate of charge in the rear electric field 172a is decreased and the amount of electrons moving to the second electrode 142 is increased.

In an alternative example, when the substrate 110 has a p-type conductivity type, the conductivity types of the plurality of emitter portions 121a and the plurality of rear electric field portions 172a have opposite conductivity types as described above. The polarities of the fixed charges of the first and second rear protective parts 92a1 and 92a2 are also changed.

Therefore, when the substrate 110 has a p-type conductivity type, the plurality of first backside protection portions 92a1 positioned below the plurality of emitter portions 121a has a fixed charge of positive polarity, The plurality of second rear protective portions 92a2 positioned below the rear electric field portion 172a have a fixed charge of negative polarity. As a result, holes are pushed toward the substrate 110 and electrons are pulled toward the plurality of emitter portions 121a by the fixed charge (+) of the first rear protective portion 92a1, and the electrons are pulled toward the plurality of emitter portions 121a. Due to the fixed charge (−), the electrons are pushed toward the substrate 110 and the holes are pulled toward the plurality of rear electric field parts 172a. Thus, the amount of electrons and holes moving to the emitter part 121a that collects the electrons The amount of holes moving to the rear electric field unit 172a to collect increases.

In this case, each of the thicknesses of the first and second rear protection parts 92a1 and 92a2 may be thicker than the thicknesses of the first and second rear protection parts 921 and 922 shown in FIG. 3, for example, 1 nm. To 20 nm.

When the thickness of each of the first and second backside protective portions 92a1 and 92a2 is about 1 nm or more, the first and second backside protective portions ( 92a1, 92a2) to increase the uniformity more stable to perform the passivation function, the first and second rear protection when the thickness of the first and second rear protection parts (92a1, 92a2) is less than about 20nm It is possible to further reduce the amount of light absorbed within the first and second backside protective portions 92a1 and 92a2 without further disturbing the transfer of charge from the portions 92a1 and 92a2 to its upper layer.

As such, since the front protective part 191a and the rear protective part 192a positioned at the front and rear of the substrate 110 have a fixed charge with a predetermined polarity, the electric charges are emitted from the emitter part 121a and the rear electric field part 172a. By preventing recombination, the amount of charge transfer to the first and second electrodes 141 and 142 is greatly increased, thereby improving the efficiency of the solar cell 14.

In an alternative example, in the solar cells 13, 14 shown in FIGS. 3 and 4, the first and second backside protective portions 921 and 922, 92a1 and 92a2 may be made of intrinsic amorphous silicon instead of oxides. In this case, the first and second backside protection portions 921 and 922, 92a1 and 92a2 made of intrinsic amorphous silicon, which are amorphous semiconductors, are located directly on the back surface of the substrate 110 made of crystalline semiconductor.

Thus, due to the presence of the first and second backside protection portions 921 and 922, 92a1 and 92a2, when the emitter portion 121a and the backside electric field portion 172a are formed, the substrate 110, which is a crystalline semiconductor, is formed. Under the influence of the crystallization of at least a portion of the emitter portion 121a and at least a portion of the rear electric field portion 172a is prevented, thereby improving the efficiency of the solar cell by heterojunction more stably.

Next, another embodiment of the present invention will be described with reference to FIG. 5.

In the solar cell 15 illustrated in FIG. 5, a silicon oxide film 193 is present at least in part between the substrate 110 and the front surface protection part 191a.

The silicon oxide films 194a and 194b may also be formed on at least a portion between the rear surface of the substrate 110 and the first rear protective portion 92a1 and at least a portion between the rear surface of the substrate 110 and the plurality of second rear protective portions 92a2. ) Is located.

In this case, the back protection part 192a including the front protection part 191a and the first and second back protection parts 92a1 and 92a2 may be made of aluminum oxide or zinc oxide made by atomic layer deposition.

When the oxide films for the front protective part 191a and the first and second rear protective parts 92a1 and 92a2 are formed by the atomic layer deposition method, the silicon oxide films 193, 194a and 194b of the present embodiment contain silicon. The substrate 110 may be formed by bonding with an oxide for the protective portions 92a1 and 92a2.

In an alternative example, at least one of the silicon oxide film 193 located on the front surface of the substrate 110 and the silicon oxide films 194a and 194b located on the rear surface of the substrate 110 may be omitted.

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

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

In the solar cell 16 illustrated in FIG. 6, similar to FIGS. 3 and 4, the substrate 11 is made of a crystalline semiconductor, and the emitter portion located on the substrate is a heterojunction solar cell made of an amorphous semiconductor.

Such a solar cell 16 will be described in detail with reference to FIG. 6.

The solar cell 16 is positioned on the substrate 110, the front protection part 191b positioned on the front surface of the substrate 110, the emitter part 121b located on the front protection part 191b, and the emitter part 121b. The auxiliary electrode 161, the plurality of front electrodes (a plurality of first electrodes) 151 positioned on the auxiliary electrode 161, a rear protective portion 192b and a rear protective portion 192b positioned on the rear surface of the substrate 110. A rear electrode 172b positioned on the back side) and a rear electrode (second electrode) 152 positioned on the rear field portion 172b are provided.

As described above, since the solar cell 16 is a heterojunction solar cell similar to the solar cells 13 and 14 shown in FIGS. 3 and 4, the emitter portion 121b is different from the substrate 110 made of crystalline silicon. ) And the back field 172b are made of amorphous silicon containing impurities having a corresponding conductivity type.

In the present embodiment, the emitter portion 121b is entirely located on the front surface of the substrate 110, and the rear electric field portion 171b is entirely located on the rear surface of the substrate 110.

At this time, when compared to the emitter unit 121a and the rear electric field unit 172a of FIGS. 3 and 4, the emitter unit 121b and the rear electric field unit 172b have the same function as only forming positions and shapes, and thus perform the same function. Detailed description of the emitter unit 121b and the rear electric field unit 172b will be omitted.

In the present solar cell 16, the efficiency of the solar cell 16 is improved by increasing the open voltage Voc due to the heterojunction structure.

The front protection part 191b disposed between the substrate 110 and the emitter part 121b and the rear protection part 192b positioned between the substrate 110 and the rear electric field part 171b are described with the protection parts 191, 191a, Similar to 192, 192a, it is made of an oxide such as silicon oxide, aluminum oxide, or zinc oxide and performs a passivation function.

Therefore, the film uniformity and film quality of the front protective part 191b and the rear protective part 192b are improved, and the passivation effect is greatly improved since crystallization of the front protective part 191b and the rear protective part 192b is difficult. Thickness control of the front protective part 191b and the rear protective part 192b is easy.

In this case, the front protection unit 191b and the rear protection unit 192b have charges (eg, holes and electrons) moved to the front and rear surfaces of the substrate 110, respectively, and the front protection unit 191b and the rear protection unit 192b. Since it must pass through to reach the emitter portion 121b and the rear electric field portion 172b, it is preferable to have a thickness that does not affect the charge transfer to the emitter portion 121b and the rear electric field portion 172b.

In this case, as described above with reference to FIGS. 2 and 4, the front protective part 191b and the rear protective part 192b may have a fixed charge having a negative polarity or a positive polarity depending on the conductivity type of the substrate 110. . In this case, as described above, unwanted transfer of charge toward the front or rear surface of the substrate 110 is prevented, thereby reducing the amount of charge loss or the recombination rate, thereby further improving the efficiency of the solar cell 16.

 The auxiliary electrode 161 is made of a material having a good conductivity and a low specific resistance. For example, the auxiliary electrode 161 is made of a transparent conductive material such as transparent conductive oxide (TCO) such as ITO, ZnO, or the like.

The front electrodes 151 are spaced apart from each other on the auxiliary electrode 161 and extend in a predetermined direction.

The front electrodes 151 collect charges (for example, holes) that have passed through the auxiliary electrode 161 and output them to an external device.

The rear electrode 152 positioned on the rear electric field part 172b is entirely located on the rear surface of the substrate 110.

The rear electrode 152 collects the charges (eg, electrons) transferred to the rear electric field unit 172b and outputs them to an external device.

The plurality of front electrodes 151 and rear electrodes 152 include nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin (Sn), zinc (Zn), indium (In), and titanium. It may be made of at least one conductive metal material selected from the group consisting of (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials other than the above.

The auxiliary electrode 161 forms a contact resistance between the emitter portion 121b made of amorphous silicon having a high resistance value and the front electrode 151 made of a metal material, thereby reducing the series resistance value of the solar cell 16 and improving the emi. The charge transfer rate from the tab portion 121b to the plurality of front electrodes 151 is improved.

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.

11-15: solar cell 110: substrate
121, 121a, 121b: emitter portion 130: antireflection portion
141: first electrode 142: second electrode
151: front electrode 152: rear electrode
161: auxiliary electrode 171: front electric field
172, 172a, 172b: rear electric field unit 191, 191a, 191b: front protection unit
192, 192a, 192b: rear protection parts 193, 194a, 194b: silicon oxide film
921, 922, 92a1, 92a2: rear protection

Claims (27)

A substrate consisting of a crystalline semiconductor,
An emitter portion formed of an amorphous semiconductor and positioned on a rear surface of the substrate to form a pn junction with the substrate,
A first protective part disposed on the front surface of the substrate and formed of an oxide,
A first electrode positioned on the emitter part and electrically connected to the emitter part; and
A second electrode positioned on a rear surface of the substrate and electrically connected to the substrate;
And the first protective part has a fixed charge having a polarity opposite to that of the conductive type of the substrate. In claim 1,
The solar cell of claim 1, further comprising a front side electric field part disposed on the first protective part, and having an impurity of the same conductivity type and the same conductivity type as the substrate, higher than the substrate, and comprising an amorphous semiconductor. In claim 2,
The first protective part has a thickness of 1 nm to 10 nm. delete delete In claim 1,
The fixed charge of the first protective part is 1 × 10 ¹² / cm ^{2 To} 1 × 10 ¹⁵ / cm ^{2 The} solar cell. In claim 1,
And the first protective portion is made of aluminum oxide when the substrate has a p-type conductivity type, and the first protective portion is made of silicon oxide when the substrate has an n-type conductivity type. In claim 1,
The first protective part has a thickness of 3nm to 20nm solar cell. delete In claim 1,
The first protective unit is a solar cell made of silicon oxide, aluminum oxide or zinc oxide. delete In claim 1,
And a backside electric field part spaced apart from the emitter part on the rear surface of the substrate and containing impurities of the same conductivity type as the conductive type of the substrate and made of an amorphous semiconductor. The method of claim 12,
And a second protection portion having a first protection portion located between the substrate and the emitter portion and a second protection portion located between the substrate and the backside electric field portion. In claim 13,
And the first protective portion and the second protective portion each have a thickness of 1 nm to 10 nm. In claim 13,
And the first protective portion and the second protective portion each have a fixed charge. 16. The method of claim 15,
The solar cell of claim 1 and the polarity of the fixed charge of the second protective portion are opposite to each other. 17. The method of claim 16,
The first protective portion has a fixed charge of the same polarity as the conductive type of the substrate,
And the second protective portion has a fixed charge of polarity opposite to the conductivity type of the substrate. 16. The method of claim 15,
And the first protective portion and the second protective portion each have a fixed charge of 1 × 10 ¹² / cm ² to 1 × 10 ¹⁵ / cm ² . 16. The method of claim 15,
And the first protective portion and the second protective portion each have a thickness of 3 nm to 20 nm. A substrate consisting of a crystalline semiconductor,
An emitter portion formed of an amorphous semiconductor and positioned in front of the substrate to form a pn junction with the substrate,
A first protective part disposed on the front surface of the substrate and formed of an oxide,
A first electrode positioned on the emitter part and electrically connected to the emitter part; and
A second electrode positioned on a rear surface of the substrate and electrically connected to the substrate;
And the first protective part has a fixed charge having a polarity opposite to that of the conductive type of the substrate. 20. The method of claim 20,
And the first protective part is located between the emitter part and the substrate. delete 20. The method of claim 20,
And a second protective part disposed on a rear surface of the substrate and formed of an oxide. The method of claim 23,
The second protective part is a solar cell made of silicon oxide, aluminum oxide or zinc oxide. The method of claim 23,
A rear electric field part disposed on the second protection part and made of an amorphous semiconductor,
And the second electrode is electrically connected to the substrate through the back field. The method of claim 23,
And the second protective part has a fixed charge of opposite polarity to the conductive type of the substrate. The method of claim 26,
Further comprising a rear electric field portion made of an amorphous semiconductor on the second protective portion,
And the second electrode is electrically connected to the substrate through the back field.

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