KR100971739B1 - Method For Manufacturing Solar Cell - Google Patents

Abstract

A solar cell manufacturing method is disclosed in which the doping concentration of the light absorbing layer is less than or equal to a predetermined value in a simple manner. Method for manufacturing a solar cell 100 according to the present invention comprises the steps of forming a first silicon layer 120 of the first conductivity type on the substrate 110; Forming a second silicon layer (130) of a first conductivity type on the first silicon layer (120); And forming a third silicon layer 140 of the second conductivity type on the second silicon layer 130, wherein the second silicon layer 130 has a predetermined doping concentration. ) The supply of dopant is stopped for a predetermined time during the formation process.

Solar Cell, Silicon, Polycrystalline, Doping Concentration, Low Doping, Dopant Supply

Description

Solar cell manufacturing method {Method For Manufacturing Solar Cell}

The present invention relates to a solar cell manufacturing method. More specifically, the present invention relates to a method for manufacturing a solar cell in which the doping concentration of the light absorbing layer is set to be equal to or less than a predetermined value in a simple manner.

Solar cells are a key component of solar power, which converts sunlight directly into electricity, and its application ranges from space to home.

A solar cell is basically a diode composed of a pn junction and its operation principle is as follows. When solar light having energy greater than the energy band gap of a semiconductor is incident on a pn junction of a solar cell, electron-hole pairs are generated, and electrons are n-layers and holes are p-layers by an electric field formed at the pn junction. As it moves, photovoltaic power is generated between pn. At this time, if a load or a system is connected to both ends of the solar cell, current flows to produce power.

Solar cells are variously classified according to materials used as light absorbing layers, and silicon-based solar cells using silicon as light absorbing layers are typical. Silicon-based solar cells are classified into substrate type (single crystal, poly crystal) solar cells and thin film type (amorphous, poly crystal) solar cells. Other types of solar cells include CdTe and CIS (CuInSe ₂ ) compound thin film solar cells, III-V solar cells, dye-sensitized solar cells, organic solar cells, and the like.

The single crystal silicon substrate type solar cell has an advantage of significantly higher conversion efficiency than other types of solar cells, but has a fatal disadvantage of high manufacturing cost by using a single crystal silicon wafer. In addition, polycrystalline silicon substrate-type solar cells may also be cheaper to manufacture than monocrystalline silicon substrate-type solar cells. However, since solar cells are made from bulk raw materials, the cost of raw materials is high and the process is high. Due to its complexity, manufacturing costs can be limited.

In order to solve the problems of the substrate-type solar cell, a thin-film silicon solar cell that can significantly lower the manufacturing cost by using a thin film of silicon as the light absorption layer on a substrate such as glass is attracting attention. Thin-film silicon solar cells can be manufactured with a solar cell having a thickness of about 1/100 of the substrate-type silicon solar cell.

Amorphous silicon thin film solar cells are the first among thin film silicon solar cells that have been developed and are now being used for home use. Amorphous silicon solar cells have the advantage of being able to form amorphous silicon by chemical vapor deposition, which is suitable for mass production and inexpensive to manufacture, but the conversion efficiency is too low compared to substrate type silicon solar cells. There is this.

Since the polycrystalline silicon thin film solar cell uses polycrystalline silicon as the light absorption layer, the solar cell has better characteristics than the amorphous silicon thin film solar cell using amorphous silicon as the light absorption layer. However, a polycrystalline silicon thin film solar cell has a disadvantage in that it is not easy to manufacture polycrystalline silicon.

On the other hand, as mentioned above, since the solar cell is basically a diode composed of a pn junction, intrinsic by adding a dopant (impurity) to increase the concentration of the electron (electron) or hole (hole) to manufacture the solar cell A doping process to make silicon into n-type or p-type silicon is indispensable.

In particular, the light absorbing layer disposed between the pn junctions of the thin film silicon solar cell needs to be doped to a predetermined concentration or less. The lower the doping concentration of the light absorbing layer, the larger the internal electric field of the light absorbing layer, and the more stable the carriers (electrons, holes) move, and the lower the doping concentration of the light absorbing layer, the lower the probability of recombination of carriers (electrons, holes) This is because the efficiency of the solar cell can be improved. In general, in consideration of various characteristics of the solar cell, the doping concentration of the light absorbing layer of the thin-film silicon solar cell is advantageously about 1 × 10 ¹⁶ / cm ³ or less.

However, according to conventional doping methods, such as diffusion doping or in situ doping, it is easy to dope at a relatively high doping concentration, but a low doping concentration of 5x10 ¹⁶ / cm ³ or less There was a limitation that it was not easy to dope with. In addition, according to the ion implantation method, which is one of the conventional doping methods, the doping concentration can be precisely controlled, so that it is possible to do the low doping concentration of ⁵ × 10 ¹⁶ / cm ³ or less. Since the time and cost of the doping process increases, there is a problem that it is difficult to apply to the mass production process of the thin film silicon solar cell.

Accordingly, the present invention has been made to solve the above-described problems, the solar cell manufacturing method to stop the dopant supply for a predetermined time during the formation of the light absorbing layer so that the doping concentration of the light absorbing layer is below a predetermined value. The purpose is to provide.

In addition, an object of the present invention is to provide a solar cell manufacturing method applicable to mass production process.

In order to achieve the above object, the solar cell manufacturing method according to the present invention comprises the steps of forming a first silicon layer of the first conductivity type on the substrate; Forming a second silicon layer of a first conductivity type on the first silicon layer; And forming a third silicon layer of a second conductivity type on the second silicon layer, wherein the dopant is supplied during the formation of the second silicon layer so that the second silicon layer has a predetermined doping concentration. It is characterized by stopping for a time.

And, in order to achieve the above object, the solar cell manufacturing method according to the present invention comprises the steps of forming a first silicon layer of the first conductivity type on the substrate; Forming a second silicon layer of a second conductivity type on the first silicon layer; And forming a third silicon layer of a second conductivity type on the second silicon layer, wherein the dopant is supplied during the formation of the second silicon layer so that the second silicon layer has a predetermined doping concentration. It is characterized by stopping for a period of time.

The substrate may comprise glass, plastic, silicon, metal, stainless steel.

When the first conductivity type is n-type, the second conductivity type may be p-type, and when the first conductivity type is p-type, the second conductivity type may be n-type.

At least one layer of the first, second and third silicon layers may be a polycrystalline silicon layer.

The method of forming the first, second and third silicon layers may include low pressure chemical vapor deposition, plasma chemical vapor deposition, and hot ray chemical vapor deposition.

The predetermined doping concentration may be 1 × 10 ¹⁶ / cm ³ or less.

The supply of the dopant can be interrupted at a predetermined cycle.

According to the present invention, the supply of the dopant is stopped for a predetermined time during the process of forming the light absorbing layer, so that the light absorbing layer has a doping concentration of less than a predetermined concentration.

In addition, according to the present invention, the supply of the dopant is stopped for a predetermined time during the process of forming the light absorbing layer, so that the light absorbing layer has a doping concentration of less than a predetermined concentration, thereby improving various characteristics of the solar cell.

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a configuration of a solar cell 100 according to an embodiment of the present invention.

Referring to FIG. 1, the solar cell 100 according to the exemplary embodiment of the present invention has an n + type silicon layer 120, an n− type silicon layer 130, and a p + type silicon layer 140 on a substrate 110. It may be a structure laminated sequentially. For reference, FIG. 1 omits the transparent conductive film, the electrode, etc. necessary for the configuration of the solar cell in addition to the three silicon layers.

The substrate 110 is preferably made of a transparent material to absorb sunlight, and may include, for example, glass or plastic. 1 illustrates a structure in which sunlight is incident from the lower side of the substrate 110, but the structure of the solar cell of the present invention is not necessarily limited thereto. This may include an incident structure. In this case, the material of the substrate 110 does not necessarily need to be a transparent material. For example, a substrate of an opaque material such as silicon, metal, stainless steel, or the like may be used.

Three layers of the silicon layer, that is, the n + type silicon layer 120, the n− type silicon layer 130, and the p + type silicon layer 140 are sequentially stacked on the substrate 110. To form a structure. Herein, the nip structure is a dopant (impurity) is low doped between the n + type silicon layer 120 doped high (p) and the p + type silicon layer 140 doped high (p) As compared to the n + -type silicon layer 120 and the p + -type silicon layer 140 refers to a structure for forming a relatively insulating n-type silicon layer 130.

As described above, the nip structure as the basic structure of the solar cell has been described in the present invention, but the present invention is not limited thereto, and a pin structure, that is, a structure in which a p + type silicon layer / p-type silicon layer / n + type silicon layer is laminated is also illustrated. It is possible.

In addition, according to the above, in the present invention, the conductivity type of the silicon layer on the i side of the solar cell is the same as the conductivity type of the silicon layer in contact with the substrate, but is not necessarily limited thereto. The solar cell may be configured by setting the conductivity type different from that of the silicon layer in contact with the substrate.

Therefore, in view of the constitution of the solar cell of the present invention, an n + type silicon layer / n-type silicon layer / p + type silicon layer, an n + type silicon layer / p-type silicon layer / p + type silicon layer, The configurations of the p + type silicon layer / p-type silicon layer / n + type silicon layer, the p + type silicon layer / n-type silicon layer / n + type silicon layer are all possible.

Hereinafter, a description will be given based on the n + type silicon layer 120 / n-type silicon layer 130 / p + type silicon layer 140 which is the configuration of FIG. 1.

Meanwhile, in the solar cell 100, at least one of the n + type silicon layer 120 / the n type silicon layer 130 and the p + type silicon layer 140 is preferably a polycrystalline silicon layer. More preferably, all of the n + type silicon layer 120 / n-type silicon layer 130 / p + type silicon layer 140 is a polycrystalline silicon layer. Polycrystalline silicon thin-film solar cell has the advantage that it is possible to drastically reduce the price through mass production by using thin-film solar cell manufacturing process as raw material of silicon having abundant abundance, and at the same time, polycrystalline silicon itself has higher electron mobility than amorphous silicon. Therefore, the efficiency of the solar cell can be improved.

The manufacturing method of the solar cell 100 according to an embodiment of the present invention is as follows.

First, the substrate 110 is prepared. As described above, the substrate 110 may include glass, plastic, silicon, metal, stainless steel, or the like. In addition, the substrate surface may be textured to improve the efficiency of the solar cell.

Next, the n + type silicon layer 120 / n-type silicon layer 130 / p + type silicon layer 140 is sequentially formed on the substrate 110. The three silicon layers are formed in an amorphous silicon state, and methods of forming the silicon layers include low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, and hot ray chemical vapor deposition. Hot Wire Chemical Vapor Deposition) method and the like.

In addition, n-type or p-type doping of the three silicon layers 120, 130, and 140 may be performed in situ during the formation of the amorphous silicon layer. In this case, it is common to use phosphorus (P) as the dopant for n-type doping and boron (B) or arsenic (As) as the dopant for p-type doping. As the thickness and doping concentration of the three silicon layers 120, 130 and 140, it is preferable to apply the thickness and doping concentration employed in a conventional silicon thin film solar cell having an n-i-p structure.

In particular, according to an embodiment of the present invention, the doping concentration of the n-type silicon layer 130 is about 1 × 10 ¹⁶ / cm ³ or less, which is a concentration advantageous for improving various characteristics of the solar cell, for example. For example, the dopant may be stopped for a predetermined time during the formation of the n-type silicon layer 130. In this case, the supply of the dopant may be stopped periodically at predetermined time intervals. That is, the supply of dopant may be interrupted periodically.

Such interruption of the dopant is, for example, when the amorphous silicon layer is formed by plasma chemical vapor deposition, when the dopant is supplied, the doping gas is mixed with the source gas containing silicon and supplied into the chamber, and when the dopant is not supplied, It can be carried out by adopting a method of supplying only the source gas containing the recone into the chamber.

Specific formation conditions of the n-type silicon layer 130 to which the doping method is applied as described above may be changed depending on the thickness of the n-type silicon layer, etc., but the n-type silicon layer commonly adopted in the thin film silicon solar cell is used. In consideration of the thickness of (i) while the dopant is stopped, SiH ₄ / H ₂ = 200 sccm / 600 sccm and the deposition pressure is 2 in supplying SiH ₄ and H ₂ gas containing silicon. torr, the deposition power is 25 watt, the deposition temperature may be 300 ℃, feed rate in the gas of SiH ₄ and H ₂ and the dopant of PH ₃ containing silicon while supplying a dopant (ii) the tray is SiH ₄ / H ₂ / PH ₃ = 200 sccm / 600 sccm / 1 sccm, the deposition pressure is 2 torr, the deposition power is 25 watt, the deposition temperature may be 300 ℃.

2 conceptually illustrates a structure of an n-type silicon layer 130 formed by a doping method according to an embodiment of the present invention.

Referring to FIG. 2, an intrinsic silicon layer 132 is stacked while the dopant is stopped and low doped at a typical doping concentration (eg, 5 × 10 ¹⁶ / cm ³ ) during the dopant supply. An n-type silicon layer 134 is stacked. In addition, since the supply of the dopant may be interrupted periodically, the lamination process may be repeated periodically. For example, in the case where the total thickness of the n-type silicon layer 130 is 1 μm, the intrinsic silicon layer 132 / n-type silicon layer 134 has a thickness of 900 Å / 100 Å or 500 Å / 500 반 repeatedly It can be stacked and formed. That is, as shown, by controlling the dopant supply or not to form a 900 Å / 100 Å or 500 Å / 500 진 intrinsic silicon layer 132 / n-type silicon layer 134 and repeat this process 10 times An n-type silicon layer 130 having a thickness of 1 μm may be formed. However, the present invention is not limited thereto and may be appropriately changed within a range capable of achieving the object of the present invention.

Next, the n + type silicon layer 120 / n-type silicon layer 130 / p + type silicon layer 140 formed in an amorphous state is crystallized to form the n + type silicon layer 120 / n-type silicon layer in a polycrystalline state. The step (130) / p + type silicon layer 140 is formed. The crystallization heat treatment process may be performed using a conventional annealing furnace, and the crystallization heat treatment conditions are preferably in a range of 400 to 700 ° C. and a heat treatment time of 1 to 10 hours.

Meanwhile, in the crystallization process of the silicon layers 120, 130, and 140, the dopant present in the n-type silicon layer 134 doped at a typical doping concentration (for example, 5 × 10 ¹⁶ / cm ³ ) is an intrinsic silicon layer ( As a result, the overall average doping concentration of the n-silicon layer 130 may be preferably adjusted to ¹ × 10 ¹⁶ / cm ³ or less. It is estimated that such a doping concentration of ¹ × 10 ¹⁶ / cm ³ or less can never be easily obtained by using a conventional doping method.

On the other hand, while the solar cell of a single junction (single junction) comprising a single nip silicon layer as an embodiment of the present invention has been described above, but not necessarily limited to, for example, two so-called tandem (tandem) structure Embodiments of the present invention also include a double junction solar cell including three nip silicon layers and a triple junction solar cell including three nip silicon layers.

As described above, the method of manufacturing the silicon thin film solar cell 100 according to the present invention stops the supply of the dopant for a predetermined time during the process of forming the n-type silicon layer 130 corresponding to the light absorbing layer of the solar cell. By adopting it, there is an advantage that the doping concentration of the n-type silicon layer 130 can be adjusted to be less than a predetermined concentration simply and easily. In particular, the above method can be directly applied to the mass production process of the solar cell, the performance of the solar cell can be improved and the manufacturing cost of the solar cell can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken in conjunction with the present invention. Variations and changes are possible. Such modifications and variations are intended to fall within the scope of the invention and the appended claims.

1 is a diagram illustrating a configuration of a solar cell 100 according to an embodiment of the present invention.

2 conceptually illustrates a structure of an n-type silicon layer 130 formed by a doping method according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: solar cell

110: substrate

120: n + type silicon layer

130: n-type silicon layer

132: intrinsic silicon layer

134: n-type silicon layer

140: p + type silicon layer

Claims (8)

Forming a first silicon layer of a first conductivity type on the substrate; Forming a second silicon layer of a first conductivity type on the first silicon layer; And Forming a third silicon layer of a second conductivity type on the second silicon layer; Including, The method of manufacturing a solar cell, characterized in that the supply of the dopant is interrupted at predetermined intervals during the formation of the second silicon layer so that the second silicon layer has a predetermined doping concentration. Forming a first silicon layer of a first conductivity type on the substrate; Forming a second silicon layer of a second conductivity type on the first silicon layer; And Forming a third silicon layer of a second conductivity type on the second silicon layer; Including, The method of manufacturing a solar cell, characterized in that the supply of the dopant is interrupted at predetermined intervals during the formation of the second silicon layer so that the second silicon layer has a predetermined doping concentration. The method according to claim 1 or 2, The substrate is a solar cell manufacturing method characterized in that it comprises glass, plastic, silicon, metal, stainless steel. The method according to claim 1 or 2, And wherein the second conductivity type is p-type when the first conductivity type is n-type, and wherein the second conductivity type is n-type when the first conductivity type is p-type. The method according to claim 1 or 2, At least one layer of the first, second and third silicon layers is a polycrystalline silicon layer. The method according to claim 1 or 2, The method of forming the first, second and third silicon layers includes a low pressure chemical vapor deposition method, a plasma chemical vapor deposition method, a hot ray chemical vapor deposition method. The method according to claim 1 or 2, The predetermined doping concentration is a solar cell manufacturing method, characterized in that less than 1 × 10 ¹⁶ / cm ³ . delete

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