KR20160047759A - Method of fabrication and structure for multi-junction solar cell formed upon separable substrate - Google Patents

Abstract

The present invention relates to a structure for multi-junction solar cells in which multiple solar cell layers are formed on a separable substrate, which grows the structure for the multi-junction solar cells separated during epitaxial growth on the separable substrate, and a method of manufacturing the same. The method comprises the steps of: installing a separable semiconductor substrate; forming a sacrificial layer on the separable semiconductor substrate; forming a solar cell portion including a plurality of III-V multi-junction solar cell layers on the sacrificial layer; forming a stabilization cell layer formed of a semiconductor compound on the solar cell portion corresponding to the outside of the III-V multi-junction solar cell layers, wherein the stabilization cell layer is formed to have a certain thickness greater than that of any one of the III-V multi-junction solar cell layers, and includes a p-doped layer and an n-doped layer formed of a germanium (Ge) material; patterning the solar cell portion and the stabilization cell layer together such that a plurality of patterning cell segments can be fully separated from each other by gaps; and etching the sacrificial layer to remove it such that the solar cell portion can be separated from the separable semiconductor substrate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a multi-junction solar cell having a plurality of solar cell layers formed on a separable substrate,

The present invention relates to a structure of a multi-junction solar cell and a manufacturing method thereof. More particularly, the present invention relates to a structure of a multi-junction solar cell, The present invention relates to a structure of a multi-junction solar cell in which a solar cell layer of a solar cell is formed.

Solar cells are a key element of solar power generation that converts solar energy directly into electrical energy. The principle of a solar cell is that when sunlight having an energy larger than the energy bandgap of a semiconductor is incident on a pn junction of a semiconductor, an electron-hole pair is generated in the junction, and the electrons- And holes are collected in the n-layer, a potential difference is generated in the pn junction.

These solar cells are only about 20% of the products that have the best efficiency among commercialized products, and the electricity production cost of solar power generation is very high. Therefore, in order to realize the solar power generation system, the efficiency of the solar cell must be increased to lower the production cost of the electric energy of the whole solar power generation. Therefore, researches for developing a high efficiency solar cell are actively conducted worldwide.

One of the ways to increase the efficiency of solar cells is to fabricate solar cells with a multi-junction structure. As a multi-junction solar cell that makes more efficient use of solar spectrum, indium gallium phosphorus / gallium arsenide / germanium InGaP / GaAs / Ge) triple junction solar cell. Such a III-V compound semiconductor junction solar cell increases the theoretical limit of conversion efficiency as the number of junctions increases.

The germanium (Ge) solar cell in the lower layer of the triple junction solar cell structure is generally manufactured by an epitaxial method of forming pn junction by diffusing arsenic (As) or phosphorus (P) atoms on a p-type germanium do.

However, silicon materials, which account for more than 95% of these solar cells, are difficult to manufacture at US $ 1 per watt, which is the production cost target of solar cells due to a shortage of supply. The manufacturing cost of the solar cell is greatly influenced by the amount of silicon used because the thickness of the silicon substrate is increased by 95% to ensure structural stability and durability against the physical impact during the manufacturing process.

A related prior art is Korean Patent Publication No. 2010-0090181 (published on Aug. 13, 2010).

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a solar cell, in which a plurality of III-V multiple junction solar cells are formed on a reusable and detachable substrate, The present invention provides a structure of a multi-junction solar cell in which a plurality of solar cell layers are formed on a detachable substrate having structural stability and durability, and a manufacturing method thereof.

In addition, the present invention can form a solar cell with a delay time by stacking several layers of solar cell structures by one epitaxial growth, thereby forming a plurality of solar cell layers on a detachable substrate And a method of manufacturing the same.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

According to another aspect of the present invention, there is provided a method of manufacturing a multi-junction solar cell including a plurality of solar cell layers on a removable substrate, the method comprising the steps of: (a) Forming a sacrificial layer on the sacrificial layer; (c) forming a portion of the solar cell including a plurality of III-V multi-junction solar cell layers on the sacrificial layer; (d) Forming a stabilizing cell layer made of a semiconductor compound on a portion of the solar cell corresponding to the outside of the III-V multiple junction solar cell layers, wherein the stabilizing cell layer has a predetermined thickness Doped layer of germanium (Ge), and (e) forming a photoresist layer over the photovoltaic layer and the stabilization layer to expose an upper portion of the sacrificial layer. Forming a gap as an empty space inside the cell layer, wherein the gap penetrates the solar cell layer and the stabilization cell layer vertically and at least one is formed extending in the transverse direction according to the shape of the pattern, Patterning the stabilizing cell layer together with a portion of the solar cell so that each of the cell segments is completely isolated from each other; and (f) etching to remove the sacrificial layer so that a portion of the solar cell is separated from the substrate .

Specifically, the stabilizing cell layer may have a predetermined thickness, preferably larger than 5 mu m.

Specifically, the sacrificial layer, the portion of the solar cell, and the stabilizing cell layer may be formed by an epitaxial growth technique, respectively.

In particular, the step (e) may further include diffusing the etching material through the gap to the exposed upper portion of the sacrificial layer.

More specifically, the step (e) may include a step of forming a metal electrode layer on which the conductive metal electrode layer is disposed on the stabilized cell layer of the patterned cell segment, and a carrier having a plurality of holes patterned so as to communicate with at least the gap, May be collectively formed on the metal electrode layer of the cell segment.

Specifically, the metal electrode layer on which the conductive pattern is formed may be formed on the exposed surface of the portion of the solar cell of the patterned segment.

Specifically, the sacrificial layer may include any one material selected from the group consisting of aluminum arsenic (AlAs) and aluminum gallium arsenide (AlGaAs).

Specifically, the substrate may include at least one material selected from the group consisting of gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP).

(B) forming a plurality of sacrificial layers and a plurality of III-V multi-junction solar cell layers on the substrate to form a plurality of sacrificial layers, And (c) forming a stabilizing cell layer made of a semiconductor compound on the top of the solar cell construct corresponding to the outside of the III-V multi-junction solar cell layer, Doped and n-doped layers of germanium (Ge) material, formed to have a predetermined thickness greater than any one of the individual ones of the -V multi-junction solar cell layers; and (d) forming a gap, which is an empty space, inside the solar cell layer and the stabilizing cell layer so that the top of the sacrificial layer is exposed, the gap penetrating the solar cell layer and the stabilizing cell layer up and down Patterning a portion of the solar cell and a stabilizing cell layer together so that each of the plurality of patterned cell segments is completely separated from each other by extending in the transverse direction according to the shape of the pattern, Etching the sacrificial layer to remove the sacrificial layer located at the uppermost position so that a part of the solar cell located in the solar cell is separated; and (f) performing the step (c) to form the stabilizing cell layer on a portion of the solar cell (G) forming a metallic second electrode on a portion of the separated top solar cell and providing a non-reflective coating; and (e) depositing a portion of the solar cell Repeating the above steps from the first step (a) until all of them are separated.

Specifically, the stabilizing cell layer may have a predetermined thickness, preferably larger than 5 mu m.

Specifically, the sacrificial layer, a portion of the solar cell, and the stabilizing cell layer may be formed by an epitaxial growth technique, respectively.

In particular, the step (d) may further include diffusing the etching material through the gap to the exposed upper portion of the sacrificial layer.

Specifically, in the step (d), a metal electrode layer to be electrically conductive is disposed on the stabilizing cell layer of the patterned cell segment, and a carrier having a plurality of holes patterned so as to communicate with at least the gap is patterned May be collectively formed on the metal electrode layer of the cell segment.

Specifically, the metal electrode layer on which the conductive material is formed may be formed on the exposed surface of the solar cell portion of the patterned segment, respectively.

Specifically, the sacrificial layer may include any one material selected from the group consisting of aluminum arsenic (AlAs) and aluminum gallium arsenide (AlGaAs).

Specifically, the substrate may include at least one material selected from the group consisting of gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP).

As described above, according to the present invention, a plurality of multi-junction solar cells are manufactured on a detachable substrate, so that the solar cell has structural stability and durability during the manufacturing process and the use period, and the energy conversion efficiency is improved and the lower frequency range of the solar spectrum There is an effect of having a frequency sensitivity that can be included.

In addition, since epitaxial growth grows into a structure of two or more multi-junction solar cell layers, rather than a structure of one multi-junction solar cell layer, production efficiency in the solar cell manufacturing process can be increased, The manufacturing cost can be reduced by increasing the number of solar cells that can be manufactured per sheet.

FIG. 1 (a) is a schematic view showing the structure of one solar cell layer according to an embodiment of the present invention. FIG.
Fig. 1 (b) is a schematic view showing the structure of the solar cell element in the next manufacturing step of Fig. 1 (a).
2 (a) is a schematic view showing a plan view and an arrangement of a patterned solar cell segment.
Fig. 2 (b) is a schematic view showing the arrangement of the carrier in the plan view of the carrier in the next manufacturing step of Fig. 2 (a).
FIG. 2 (c) is a schematic view showing a segment of the solar cell cell separated in the next manufacturing step of FIG. 2 (b).
FIG. 2 (d) is a schematic view showing an actual use example of the solar cell segment in the next manufacturing step of FIG. 2 (c).
3 (a) is a schematic view showing the structure of a plurality of solar cell layers according to another embodiment of the present invention.
Fig. 3 (b) is a schematic view showing the structure of the solar cell element in the next manufacturing step of Fig. 3 (a).
4 (a) is a schematic plan view of the patterned solar cell segment and its arrangement.
Fig. 4 (b) is a schematic view showing the arrangement of the carrier in a plan view in the next manufacturing step of Fig. 3 (a).
Fig. 4 (c) is a schematic view showing the separation of the topmost layer solar cell segment in the next fabrication step of Fig. 3 (b).
4 (d) is a schematic view showing Ge epitaxial growth after separation of the topmost layer solar cell segment in the next fabrication step of FIG. 3 (c).
Fig. 4 (e) is a schematic view showing a segment of the solar cell cell separated in the next manufacturing step of Fig. 2 (d).
4 (f) and 4 (g) are schematic views showing examples of actual use of the solar cell segment in the next manufacturing step of FIG. 2 (e).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Among the types of easily available solar cells, III-V multi-junction solar cells generally have the highest conversion efficiency. However, the fabrication cost of III-V multi-junction solar cells tends to be relatively high compared to other types of solar cells. This is because the III-V multi-junction solar cell film is generally grown on an expensive substrate made of a semiconductor compound such as gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP). To save manufacturing costs, these expensive substrates need to be reused because expensive substrates are only needed to obtain high-quality epitaxial layers. That is, these expensive substrates do not form a functional component in the solar cell device, and the role of the thin film solar cell film necessary for the stage after the growth is completed is no longer required.

After the epitaxial growth of the device layers serving as a function of the solar cell is completed, the substrate can be separated for reuse via a selective etching process. For this purpose, a sacrificial layer is grown between the solar cell thin film layer and the gallium arsenide (GaAs) substrate and only the sacrificial layer is selectively etched away without etching the solar cell thin film or substrate material . This etch process is commonly referred to as an epitaxial-lift-off ELO technique. The sacrificial layer for the III-V solar cell film is a single-crystal AlAs layer or an AlGaAs layer, which is placed on a gallium arsenide (GaAs) substrate. After an additional manufacturing process such as formation of a solar cell layer and formation of a metal electrode layer, the grown wiper is contained in a hydrogen fluoride (HF) solution. The hydrogen fluoride (HF) solution selectively etches the aluminum arsenide (AlAs) sacrificial layer. After the aluminum arsenic (AlAs) sacrificial layer is completely removed by selective etching, the substrate and the III-V solar cell film are separated. The separated solar cell film may be bonded to a suitable carrier compound material for subsequent processing. These carrier compounds may be made of materials such as plastic, glass, ceramic, metal or semiconductor.

Generally, the thickness of the III-V solar cell film is several 탆. Therefore, it is very difficult to separate such a thin solar cell film from the substrate by itself. These thin films are also easily damaged. Therefore, the thin film must be bonded onto a suitable carrier before being immersed in a hydrogen fluoride (HF) solution, etched, and separated from the substrate. Since the material of the carrier and the material of the binder are influenced by the fluorine solution together with the thin film during the course of the epitaxial lift-off ELO, the material of the carrier and the material of the binder are changed by the hydrogen fluoride (HF) solution The one that can withstand the etching is selected.

There are the following problems related to the epitaxial-lift-off ELO technique.

That is, since the structure of a multi-junction III-V solar cell up to now is made up of only a few microns of III-V compound, it is too thin to be applied to many applications even when bonded to a carrier, Which is very vulnerable. That is, the thermal expansion coefficient of a thin film made of a III-V compound generally does not coincide with the thermal expansion coefficient of a typical carrier compound. And during use in a variety of environments, both in the manufacturing process and in the thin film film, the thermal cycle remains unchanged. If the thermal expansion coefficient of the solar cell thin film is different from the thermal expansion coefficient of the carrier compound, stress is generated in the thin film, and if the thin film can not withstand such stress, the thin film becomes defective until cracking occurs .

At this time, the bonding material used for bonding the carrier and the thin film together with the carrier compound may reduce the stress generated on the thin film. Generally, the bonding material is provided in the form of a liquid or gel during the bonding process and hardened after the bonding process. Once the bonding material has hardened, shrinkage occurs in volume. This reduction in volume creates compressive stress on the thin film of III-V compound, which immediately leads to defects, resulting in cracks around the edge of the film. The stress generated on the thin film depends on the volume of the bonding material and the area where the thin film is in contact with the bonding material layer.

The thin film of III-V compound solar cell of several ㎛ is very vulnerable to the stress generated from the above carrier and bonding material. This means that it is very difficult to achieve the desired level of reliability. Despite these difficulties, various approaches have been developed to improve reliability. For example, increasing the thickness of the thin film may be considered. However, this would increase the cost of growing the III-V compound film. In addition, the cost required to grow a thin film of sufficient thickness to eliminate the risk to reliability is likely to exceed the cost of expensive substrates, resulting in cost savings due to epitaxial-lift-off ELO Anything becomes meaningless.

Another problem in the epitaxial-lift-off ELO technique is the problem of increased energy conversion efficiency. In order to obtain a high efficiency in energy conversion, it is desirable that the sensitivity of the III-V compound of the solar cell thin film film reacts in all spectral regions of the sunlight. Thus, the III-V reacting in the low frequency region of the solar spectrum The compound is also present. However, such compounds that can provide a sufficiently low solar spectrum frequency coverage area tend to have lattice constants that are larger than the lattice constants of gallium arsenide (GaAs) substrates. A thick buffer layer is required to grow compounds with different lattice constants on a gallium arsenide (GaAs) substrate. However, despite this, it can be very difficult to obtain high reliability. Also, as the thickness of the buffer layer increases, the manufacturing cost of all solar cells increases, making it difficult to apply to most epitaxial-lift-off ELO applications. The gain of energy conversion efficiency by this approach is also limited because the number of different lattice-constant layers that can be actually inserted into the solar cell structure is limited.

Even with such problems, epitaxial-lift-off ELO is a very effective technique for reducing the manufacturing cost of III-V compound solar cells. However, as described above, the problem of reliability still exists, and the room for improvement in energy conversion efficiency is also limited. Increasing the film thickness of the III-V compound to solve the problem of reliability also increases the manufacturing cost, and consequently the epitaxial-lift-off ELO technique used as a method to reduce the manufacturing cost It becomes meaningless.

It can be seen that this reliability problem and energy conversion problem are addressed together according to certain aspects of the present invention with respect to epitaxial-lift-off ELO. An example of a method of application of the epitaxial-lift-off ELO technique and its structure is shown in Fig. Referring to FIG. 1, the solar cell construct 10 in the solar cell manufacturing process includes a gallium arsenide (GaAs) substrate 2, aluminum arsenic (AlAs), aluminum gallium arsenide (AlGaAs) A compound III-V compound solar cell layer 6, and a germanium (Ge) stabilizing cell layer 8, all of which are made of a single layer.

Preferably, the thickness of the germanium (Ge) stabilizing cell layer 8 should be greater than 5 占 퐉. The germanium (Ge) stabilizing cell layer 8 of this thickness serves two purposes. One provides stability due to the relatively thick geranium (Ge) stabilizing cell layer 8, which results in the solar cell layer 6 being less susceptible to stresses due to the carrier and the bonding material. The other is that the material of the germanium (Ge) stabilizing cell layer 8 makes it possible to extend the frequency region responsive to the sunlight spectrum to a lower frequency region. This expansion of the frequency range also increases the energy conversion efficiency realized by the III-V multi-junction solar cell layer 6. [

Stabilization of the epitaxial germanium (Ge) stabilizing cell layer 8 can be achieved through appropriate measures for the solar cell layer 6. For example, after the growth of a III-V compound epitaxial layer, germanium (Ge) is grown by molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), chemical graft crystal growth (CBE) ) Epitaxially growing the stabilized cell layer 8, the epitaxially grown germanium (Ge) stabilized cell layer 8 can be stably and continuously grown. Another alternative method for stabilizing the epitaxially grown germanium (Ge) stabilizing cell layer 8 can be achieved by growing the III-V compound epitaxial layer in another growth chamber after growth. These alternative replaceable growth chambers can be used to derive the cost of germanium (Ge) growth, which is less than the cost of chemical vapor deposition (CVD), high vacuum chemical vapor deposition (CVD), or III-V compound growth. There are similar methods. Chemical vapor deposition (CVD) can epitaxially grow a germanium (Ge) stabilizing cell layer 8 of high quality with negligible external emission during the diffusion of gallium (Ga) and arsenic (As). V compound (s) can be prepared by epitaxial growth techniques by any suitable method known in the art, such as molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), actinic crystal growth (CBE) After the layer is first grown, the germanium (Ge) stabilizing cell layer 8 may again grow in an inexpensive growth chamber by the epitaxial method.

After the epitaxial growth of the germanium (Ge) stabilizing cell layer 8, the carrier 12 is suitably bonded to the germanium (Ge) stabilizing cell layer 8.

The process of reusing the gallium arsenide (GaAs) substrate after the thick aluminum arsenide (AlAs) sacrificial layer 4 is grown by the above-described method is as follows. First, the bonded wafers arising from the manufacturing process of the thin film are immersed in a hydrogen fluoride (HF) solution. Then, the etching starts on the exposed side of the wafer, and the etched portion is gradually moved to the central portion of the wafer. This process occurs very slowly because the etching process only occurs on the exposed side of the sacrificial layer. The slow rate of this etching process may be accelerated by using a thicker aluminum AlAs sacrificial layer 4 to increase the surface area of the side to be etched. However, this method certainly raises the upper limit of the manufacturing cost per unit area of the product. Another way to accelerate the speed of the etching process is to use a flexible carrier. Flexible carriers can assist the spreading mechanism because they may bend. However, this approach is applicable only when the carrier compound is a flexible material, and is not suitable when high reliability is required or in mass production.

According to one embodiment of the present invention, the etch process can be assisted by exposing the top surface portion of the sacrificial layer 4, which may remain covered by the other layers and not reach the etch material, to the etch material. That is, as shown in the embodiment of Figs. 2 (a) and 2 (b), in the configuration of the solar cell 100, one or more gaps 3 are formed in the patterned cell segments 10a, 10b , 10c, and 10d. These gaps 3 provide an additional path through which a hydrogen fluoride (HF) etch solution can be diffused into the aluminum arsenic (AlAs) sacrificial layer 4. Preferably the fluorine (HS) etch solution is diffused into the holes 12a, 12b, 12c, 12d formed in a given carrier 12 and coinciding with the gap 3, and then the patterned cell segments (AlAs) sacrificial layer 4 through the gap 3 between the upper and lower surfaces 10a, 10b, 10c, and 10d. If byproducts of the etching process occur after the etching process is completed, the by-products pass through the gap 3 and the holes 12a, 12b, 12c, and 12d and are diffused reversely.

Comparing this process with the prior art, the upper surface of the more AlAs sacrificial layer 4 can be initially exposed to the hydrogen fluoride (HF) etching solution. That is, the etching solution and the byproducts of the etching process can easily diffuse from or exit from the AlAs sacrificial layer 4, so that the efficiency of the etching process can be remarkably increased by this method. As shown in FIG. 2A, the cell segments 10a, 10b, 10c, and 10d and the metal electrode layers are arranged in a patterned array, or the cell segments 10a, 10b, 10c, The electrode layer can be disposed and patterned by the gap 3 using any suitable technique known in the art. As shown in Fig. 2 (a), this pattern may be a rectangle 10a, 10b, 10c, 10d or a hexagon 10'a, 10'b, 10'c, 10'd. The size of such a cell may vary and may range, for example, from about 10 microns to several centimeters. The gap 3 between the cell segments 10a, 10b, 10c and 10d is preferably less than 20% of the cell size.

The patterned wafer is preferably etched by dry etching or wet etching techniques. The compound of the germanium (Ge) stabilizing cell layer 8 and the III-V multiple junction solar cell layer 6 located at the position where the gap 3 is to be formed can be separated so as to separate the individual cell segments 10a, 10b, 10c and 10d So that the upper end portion of the aluminum arsenic (AlAs) sacrificial layer 4 is exposed to the etching material. When these portions located at the position where the gap 3 is located in the germanium (Ge) stabilizing cell layer 8 and the III-V multiple junction solar cell layer 6 are etched so that the outline of the gap 3 clearly appears, The electrode layers 9a and 9b can be placed on top of the respective cell segments 10a, 10b, 10c and 10d. Any other suitable material (not shown) may also be used as an etch mask for these materials.

When the metal electrode layers 9a and 9b are disposed after the germanium (Ge) stabilizing cell layer 8 and the III-V multi-junction solar cell layer 6 are etched, the carrier 12 is bonded to the solar cell thin- do.

As shown in FIG. 2 (b), a hydrogen fluoride (HF) etch solution is passed through the carrier 12 from the backside of the carrier 12 toward the aluminum arsenide (AlAs) sacrificial layer 4 The pattern grooves 12a, 12b, 12c, and 12d are formed so as to be able to reach. The size of the pattern grooves 12a, 12b, 12c, and 12d is formed to be similar to the size of the gap 3. If necessary, the carrier 12 may be coated with a metal, and one side of the metal may be provided on the metal electrode layers 9a and 9b serving as metal electrodes of the solar cell segments 10a, 10b, 10c and 10d, Are joined by a method such as metal soldering or the like. If a metal carrier is used, no metal coating is required. Also, if the metal electrodes formed on each patterned cell segment 10a, 10b, 10c, 10d are connected to each other, a metal coating on the carrier is also unnecessary. In such a case, the solar cell thin film and the carrier may be bonded using a material different from the solder metal.

Once such a carrier is bonded, the final bonded wafer is suitably immersed in a hydrogen fluoride (HF) etch solution and the hydrogen fluoride (HF) etch solution is agitated. Hydrogen fluoride (HF) not only contacts the exposed side of the aluminum arsenic (AlAs) sacrificial layer 4 to etch the aluminum arsenic (AlAs) sacrificial layer 4 rapidly from the multiple exposed surfaces, (12a, 12b, 12c, 12d). And the by-products of etching diffuse in the reverse fashion. After the aluminum arsenic (AlAs) sacrificial layer 4 is completely removed, the gallium arsenide (GaAs) substrate 2 is separated from the III-V multiple junction solar cell layer 6 and the germanium (Ge) do.

According to this procedure, the patterns of the second electrodes 14a and 14b can be exposed by using a photoresist according to an appropriate technique known to the manufacturer. The metal pattern is formed by a lift-off as shown in Fig. 2 (c). After the second electrode is formed, the passivation for the etched sidewalls of the cell segments 10a, 10b, 10c, 10d formed in a hexagonal or other manner is suitably performed and the surface of the final device is provided with a non-reflective ) Coating process is carried out together. Preferably an aluminum oxide (Al ₂ O ₃ ) or zinc oxide (ZnO) layer can be used for passivation and non-reflective (AR) coatings on the sidewalls. Passivation and non-reflective (AR) coatings can be completed concurrently with the use of the tilted loading type of ion-beam assisted electron beam deposition method. Finally, a non-reflective (AR) coating film formed over the electrode portion for electrical contact is removed by a mask pattern using photoresist and etching methods.

Once the fabrication process is complete, the patterned individual cell segments 10a, 10b, 10c, 10d may be cut away (dice-shaped cube) to separate from each other and, as shown by way of example in FIG. 2 (d) It is assembled with a focus lens for practical use. If a plurality of cell electrodes are connected to each other, many patterned cells can be collectively used as a single solar cell.

The above describes the structure and manufacturing method of the multi-junction solar cell structure when the multi-junction solar cell structure is formed only by one layer in the epitaxial growth of the multi-junction solar cell structure. 3 and 4, a description will be given of a structure and a manufacturing method of a multi-junction solar cell structure in which two or more plural layers are formed instead of one layer in one common substrate.

 FIG. 3 shows an example in which a multi-junction solar cell structure includes a plurality of layers in a structure of a multi-junction solar cell by applying an epitaxial-lift-off ELO technique according to the present invention. 3, the solar cell construct 200 includes a GaAs substrate 20, a sacrificial layer 40 made of aluminum arsenide (AlAs), aluminum gallium arsenide (AlGaAs), and other suitable semiconductor compounds, Further comprising a predetermined number of layers including a sacrificial layer 40 and a solar cell layer 60 including a III-V compound multi-junction solar cell layer 60 and a stabilization cell layer 80.

At this time, the division between the plurality of III-V multiple junction solar cell layers 60 can be distinguished from each other by introducing a plurality of aluminum arsenic (AlAs) sacrificial layers 40.

On the other hand, a manufacturing method when the multi-junction solar cell structure is formed of two or more plural layers instead of one layer in one common substrate includes the steps of: (a) installing a separable semiconductor substrate 20; (b) forming a plurality of sacrificial layers 40 and a plurality of III-V multi-junction solar cell layers 60 on a substrate 20 on a plurality of sacrificial layers 40 (C) forming a stabilizing cell layer (80) made of a semiconductor compound on the top of a portion of the solar cell constructor (200) corresponding to the outside of the III-V multiple junction solar cell layer (60) The cell layer 80 is formed to have a predetermined thickness greater than any one of the individual III-V multiple junction solar cell layers 60, and the p-doped and n-doped layers of germanium (Ge) (D) exposing the top of the sacrificial layer (40) to a solar cell A gap 30 which is an empty space is formed inside the layer 60 and the stabilizing cell layer 80. The gap 30 penetrates the solar cell layer 60 and the stabilizing cell layer 80 vertically, A part of the solar cell 300 and the stabilizing cell layer 80 are formed so that the plurality of patterned cell segments 200a, 200b, 200c, and 200d are completely separated from each other, (E) etching to remove the sacrificial layer 40 located at the top so that a part of the solar cell 300 located at the top is separated, (f) (C) again to form a stabilizing cell layer 80 on a portion of the car; and (g) applying a metallic second electrode 140a, 140b (E) forming a plurality of layers (e. G., ≪ RTI ID = 0.0 > Until all be made part of the solar cells 300 are separated from the start (a) of the step and a step of repeating the steps that follow.

First, when the III-V multiple junction solar cell layer 60 is a single layer, the substrate 20, the gap 30, the sacrificial layer 40, the solar cell layer 60, the stabilizing cell layer 80, The second electrodes 140a and 140b and the cell segments 200a, 200b, 200c, and 200d are formed in the process of manufacturing the solar cell 300 The kinds of the compounds constituting each of them and the growth method thereof are the same as those in the previous embodiment, and the detailed description thereof will be omitted below.

Referring to FIG. 3 (a), a substrate 20 which can be separated in step (a) is provided, and a sacrificial layer 40 and a plurality of III-V multiple junctions A solar cell construct 200 including a battery layer 60 is formed on a plurality of sacrificial layers 40, respectively.

Where the sacrificial layer 40 is epitaxially grown and the III-V multiple junction solar cell layer 60 is epitaxially grown on the sacrificial layer 40 again. After the sacrificial layer 40 and the solar cell layer 60 are formed as described above, the sacrificial layer 40 and the solar cell layer 60 are continuously formed repeatedly on the solar cell layer 60, A plurality of solar cell layers 60 are epitaxially grown. 3 (a) shows an embodiment in which three sacrificial layers 40 and a solar cell layer 60 are formed, respectively.

3 (b), after the epitaxial growth of the predetermined number of sacrificial layer 40 and the solar cell layer 60 is completed, germanium (Ge) is grown on the epitaxial multi- ) Stabilizing cell layer 80 is epitaxially grown. That is, in the step (c), a stabilizing cell layer 80 made of a semiconductor compound is formed on the top of the portion of the solar cell construct 200 corresponding to the outside of the III-V multiple junction solar cell layer 60. The stabilizing cell layer 80 is formed to have a predetermined thickness larger than the thickness of any one of the III-V multi-junction solar cell layers 60, and p-doping and n-doping of germanium (Ge) Lt; / RTI >

Referring to FIG. 4A, metal layers 90a and 90b for forming electrodes are disposed on a germanium (Ge) cell layer 80, and a III-V multi-junction solar cell layer (60) epitaxy is etched.

That is, this corresponds to the step (d), in which a plurality of solar cells 200a and 200b are formed and separated from one layer through the gap 30 to the top III-V multiple junction solar cell layer 60 epitaxy Thereby forming patterning. This patterning may be a rectangular cell segment 200a, 200b, 200c, 200d or a hexagonal cell segment 200'a, 200'b, 200'c, 200'd, The size can vary. Then, the patterned wafer is etched by dry etching or wet etching. It is the same as the description of the previous embodiment that each of the cell segments 200a, 200b, 200c, and 200d forms a plurality of solar cells.

Referring to FIG. 4B, the gap 30 is formed by etching so that the solar cell layer 60 and the germanium (Ge) stabilizing cell layer 80 are sandwiched by the respective cell segments 200a 200b, 200c and 200d and the carrier 120 is bonded onto the metal layers 90a and 90b located above the cell segments 200a, 200b, 200c and 200d.

After the carrier 120 is bonded, fluorine (HS) etching solution is injected into the gap 30 to remove the uppermost aluminum arsenic (AlAs) sacrificial layer 40 (epitaxial-lift-off ELO )).

Referring to FIG. 4C, after the sacrificial layer 40 is removed by an epitaxial-lift-off ELO technique, the top III-V multiple junction solar cells 200a and 200b are separated. That is, step (e) corresponds to etching to remove the sacrificial layer 40 located at the top so that a part of the solar cell 300 located at the top is separated.

4 (d), when the uppermost solar cell layer 60 and the sacrificial layer 40 are separated from each other, the upper III-V multi-junction solar cell layer 60 is exposed, The germanium (Ge) cell layer 80 is again epitaxially grown on the multi-junction solar cell layer 60 once again. That is, this corresponds to the step (f) of performing the step (c) again to form the stabilizing cell layer 80 on the part of the solar cell 300.

Referring to FIG. 4E, second electrodes 140a and 140b made of metal are formed on the uppermost III-V multiple junction solar cells 200a and 200b separated from the upper part, and the surfaces and the joints are appropriately treated, Passivation process and non-reflective (AR) coating for stabilizing the device characteristics. That is, this corresponds to step (g).

Referring to FIGS. 4F and 4G, after the above-described manufacturing process is completed, each of the patterned cell segments 200a, 200b, 200c, and 200d can be used as an actual solar cell .

On the other hand, a plurality of III-V multi-junction solar cell layers 60 remain after the plurality of solar cells are fabricated in one layer located at the uppermost position through the above manufacturing process, Return to the process and repeat the subsequent process. That is, the solar cell is fabricated by repeating the above steps from the first stage to the upper III-V multi-junction solar cell layer 60 on which the germanium (Ge) cell layer 80 is formed by epitaxial growth. That is, this corresponds to the step (e) of repeating the steps from the first step (a) to the subsequent steps until all the parts of the solar cell 300 having a plurality of layers from the substrate 20 are separated.

 As described in the previous embodiment, the sacrificial layer 40 and the III-V multiple junction solar cell layer 60 and the stabilizing cell layer 80, which are part of the solar cell 300, are formed by the epitaxial growth technique do. The sacrificial layer 40 may be any one selected from the group consisting of aluminum arsenide (AlAs) and aluminum gallium arsenide (AlGaAs).

In the step (c), the stabilization cell layer may be a germanium (Ge) cell layer 80, and the predetermined thickness is preferably larger than 5 탆.

In addition, (d) further includes a method of diffusing the etching material through the gap 30 to the exposed upper portion 40 'of the sacrificial layer 40.

In the step (d), the metal electrode layers 90a and 90b to be electrically conductive are disposed on the stabilizing cell layers 80 of the patterned cell segments 200a, 200b, 200c and 200d, The carrier 120 having a plurality of pattern holes 120a, 120b, 120c and 120d patterned so as to be patterned is collectively formed on the metal electrode layers 90a and 90b of the patterned cell segments 200a, 200b, 200c and 200d. Respectively. The metal electrode layers 90a and 90b are formed on exposed surfaces of a part of the solar cell 300 as patterned cell segments 200a, 200b, 200c, and 200d, respectively.

In addition, the substrate 20 includes at least one material selected from the group consisting of gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP).

The structure of the multi-junction solar cell in which a plurality of solar cell layers are formed on the detachable substrate and the method of manufacturing the same are not limited to the above-described embodiments, It is to be understood that various modifications and variations are possible insofar as all or any of the embodiments are selectively combined from such description. Accordingly, the spirit of the present invention should be understood only by the claims set forth below, and all of its equivalents or equivalent equivalents fall within the spirit of the present invention.

The substrate 20 has a gap 30,
The sacrificial layer 40, the solar cell layer 60,
Stabilizing Cell Layer (80) The metal electrode layers (90a, 90b)
The carrier 120 pattern grooves 120a, 120b, 120c,
The second electrodes 140a and 140b are connected to the solar cell structure 200,
The cell segments 200a, 200b, 200c, and 200d, the solar cell 300,

Claims (16)

(a) providing a removable semiconductor substrate;
(b) forming a sacrificial layer on the substrate;
(c) forming a solar cell portion including a plurality of III-V multi-junction solar cell layers on the sacrificial layer;
(d) forming a stabilizing cell layer made of a semiconductor compound on the solar cell portion corresponding to the outside of the III-V multi-junction solar cell layer,
The stabilizing cell layer is formed to have a predetermined thickness larger than any one of the individual III-V multiple junction solar cell layers, and is formed of a p-doped and an n-doped layer of germanium (Ge) ; ≪ / RTI >
(e) forming a gap, which is an empty space, inside the solar cell layer and the stabilizing cell layer such that an upper portion of the sacrificial layer is exposed, the gap penetrating the solar cell layer and the stabilizing cell layer vertically, Patterning the portion of the solar cell and the stabilization cell layer together so that each of the plurality of patterned cell segments is completely separated from each other by at least one extending in the transverse direction according to the shape; And
(f) etching the sacrificial layer to remove a portion of the solar cell from the substrate; and forming a plurality of solar cell layers on the removable substrate.
The method according to claim 1,
Wherein the stabilizing cell layer has a predetermined thickness greater than 5 占 퐉. A method of manufacturing a multi-junction solar cell, wherein a plurality of solar cell layers are formed on a detachable substrate.
The method according to claim 1,
Wherein the sacrificial layer, the solar cell portion, and the stabilization cell layer are formed by an epitaxial growth technique, respectively, wherein a plurality of solar cell layers are formed on the detachable substrate.
The method according to claim 1,
Wherein the step (e) further comprises diffusing the etchant through the gap to the exposed upper portion of the sacrificial layer. ≪ RTI ID = 0.0 >≪ / RTI >
The method according to claim 1,
Wherein the step (e) includes the steps of: forming a metal electrode layer on the patterned cell segment, the metal electrode layer being disposed on the stabilized cell layer of the patterned cell segment, the carrier having a plurality of holes patterned to communicate with at least the gap, Wherein the plurality of solar cell layers are formed on the separable substrate, wherein the plurality of solar cell layers are formed collectively on the metal electrode layer of the segment.
6. The method of claim 5,
Wherein the plurality of solar cell layers are formed on the detachable substrate, wherein the plurality of solar cell layers are formed on the detachable substrate.
The method of claim 3,
Wherein the sacrificial layer comprises any one material selected from the group consisting of aluminum arsenide (AlAs) and aluminum gallium arsenide (AlGaAs). Gt;
8. The method of claim 7,
Wherein the substrate comprises at least one material selected from the group consisting of gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP). A method of manufacturing a solar cell.
(a) providing a removable semiconductor substrate;
(b) forming a plurality of sacrificial layers and a plurality of III-V multi-junction solar cell layers on the plurality of sacrificial layers, respectively;
(c) forming a stabilizing cell layer made of a semiconductor compound on the top of the solar cell construct corresponding to the outside of the III-V multi-junction solar cell layer,
The stabilizing cell layer is formed to have a predetermined thickness larger than any one of the individual III-V multi-junction solar cell layers, and is formed of a p-doped and an n-doped layer of germanium (Ge) ; ≪ / RTI >
(d) forming a gap, which is an empty space, inside the solar cell layer and the stabilizing cell layer such that an upper portion of the sacrificial layer is exposed, the gap penetrating the solar cell layer and the stabilizing cell layer vertically, Patterning the portion of the solar cell and the stabilization cell layer together so that each of the plurality of patterned cell segments is completely separated from each other by at least one extending in the transverse direction according to the shape;
(e) etching to remove the sacrificial layer located at the top so that a portion of the solar cell located at the top is separated;
(f) performing the step (c) again to form the stabilizing cell layer on a portion of the solar cell;
(g) forming a metallic second electrode on the separated top solar cell portion and providing a non-reflective coating; And
(e) repeating the steps from the first step (a) until all of the solar cell parts of the plurality of layers are separated from the substrate, wherein a plurality of solar cell layers are formed on the detachable substrate Wherein the method comprises the steps of:
10. The method of claim 9,
Wherein the stabilizing cell layer has a predetermined thickness greater than 5 [mu] m, wherein the plurality of solar cell layers are formed on the detachable substrate.
10. The method of claim 9,
Wherein the sacrificial layer, the solar cell portion, and the stabilization cell layer are formed by an epitaxial growth technique, respectively, wherein a plurality of solar cell layers are formed on the detachable substrate.
10. The method of claim 9,
Wherein the step (d) further comprises diffusing an etchant through the gap to the exposed upper portion of the sacrificial layer. ≪ RTI ID = 0.0 >≪ / RTI >
10. The method of claim 9,
Wherein the step (d) comprises the steps of: forming a metal electrode layer on which a conductive metal electrode layer is formed, the metal electrode layer being disposed on the stabilizing cell layer of the patterned cell segment and having a plurality of holes patterned so as to communicate with at least the gap, Wherein the plurality of solar cell layers are formed on the separable substrate, wherein the plurality of solar cell layers are formed collectively on the metal electrode layer of the segment.
14. The method of claim 13,
Wherein the plurality of solar cell layers are formed on a detachable substrate, wherein the plurality of solar cell layers are formed on the detachable substrate.
10. The method of claim 9,
Wherein the sacrificial layer comprises any one material selected from the group consisting of aluminum arsenide (AlAs) and aluminum gallium arsenide (AlGaAs). Gt;
10. The method of claim 9,
Wherein the substrate comprises at least one material selected from the group consisting of gallium arsenide (GaAs), germanium (Ge), and indium phosphide (InP). A method of manufacturing a solar cell.

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