KR100818783B1 - Solar cells fabricated on cube-textured metallic substrate - Google Patents

Abstract

The present invention discloses a low cost solar cell by fabricating a solar cell using a cub-textured metal substrate without using a single crystal silicon substrate. The solar cell according to the present invention has higher efficiency than a solar cell using polysilicon or amorphous silicon having a random crystal direction by using a substrate in which crystals are aligned in a constant direction.

Solar cells, metal substrates, cub-texture

Description

Solar cells fabricated on cube-textured metallic substrate

1 illustrates a structure of a silicon substrate formed on an aligned metal substrate according to a first embodiment of the present invention.

2 illustrates a circuit example of a solar cell fabricated on the silicon substrate of FIG. 1,

3 shows the crystal orientation of domains in a polysilicon substrate,

4 illustrates a determination direction of domains in a semiconductor substrate according to the present invention.

5 is an example of a (100) -direction pole figure of a metal substrate used in the present invention,

6 is an example of the spatial arrangement of charges caused by mismatch between two domains,

7 shows a solar cell structure according to a second embodiment of the present invention,

8 illustrates an example of an apparatus for manufacturing a solar cell according to the present invention.

9 shows a structure of a solar cell according to a third embodiment of the present invention.

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

110, 210: Cubic aligned metal substrate 120, 220: Non-conductive ceramic layer

130: semiconductor layer 230: first type semiconductor layer

240: type 2 semiconductor layer 250, 260: transparent electrode

710: cubic aligned metal substrate 720: conductive ceramic layer

730: first type semiconductor layer 740: second type semiconductor layer

750 transparent electrode 760 antireflection film

770, 780: electrical junction

800 cylinder 810 cubic aligned metal substrate

820: ceramic thin film deposition unit 830: semiconductor layer deposition unit

840: transparent electrode deposition unit 850: reel

910: cubic aligned metal substrate 920: non-conductive ceramic layer

925: conductive ceramic or metal

930: type 1 semiconductor layer 940: type 2 semiconductor layer

950 transparent electrode 960 antireflection film

970, 980: electrical junction

The present invention relates to a solar cell formed on a cubic aligned metal substrate, and more particularly, to amorphous silicon (α-Si) or polycrystalline silicon (poly-Si) without using a single crystal silicon (Si) substrate. It relates to a solar cell which is more efficient than the solar cell used.

Solar cells are attracting much attention as an important energy source of the future because they can be used eco-friendly and semi-permanently. However, in general, highly efficient solar cells use silicon substrates, but solar cells do not require complex circuits, but due to their large area, they require expensive large-area silicon substrates, which has been a barrier to practical use. As an alternative to this, many researches have been conducted on amorphous solar cells using amorphous silicon layers formed on low-cost and amorphous substrates such as glass plates and metal plates, and solar cells formed on the amorphous silicon layers. The sensitivity to is known to be superior to that of silicon substrates. However, within amorphous silicon, broken bonds that are not completely covalently distributed randomly in space, and electron-hole pairs generated by incident light are trapped by these broken bonds and recombined to form a single crystal silicon substrate. Compared with the solar cell used, there is a disadvantage that the efficiency is significantly lower. In order to reduce the number of trap centers, a process of crystallizing amorphous silicon is required. This crystallization is a method of crystallizing partially by using a laser or the like when the substrate is used as a glass plate. There is a disadvantage that a lot of this, and the price of the process is increased. In addition, since the domains of the substrate crystallized through this process have a random direction, the reduction of the center density of the capture below a certain level cannot be expected, which is an obstacle to increasing the efficiency.

The technical problem to be achieved by the present invention is low cost because it does not use a single crystal silicon substrate, and the efficiency is high by using a method of reducing trap centers that exist in a large number as in the amorphous silicon solar cell. It is to provide a high efficiency solar cell similar to using.

The present inventors have completed the present invention by confirming that the above object can be achieved when using a cubic aligned metal thin film as a substrate of a solar cell.

Accordingly, the present invention relates to a solar cell formed on a cubic aligned metal substrate, and more particularly to a cubic aligned metal substrate; A first type semiconductor layer and a second type semiconductor layer formed on the substrate; And it relates to a solar cell comprising an electrode.

In the present invention, three solar cells having different structures according to the positions of the electrodes are provided. The first structure is a case in which one embodiment has a first type electrode formed in the first type semiconductor layer and a second type electrode connected to the second type semiconductor layer as shown in FIG. One embodiment differs from the first structure as shown in FIG. 7 in that the first type electrode is connected to the metal substrate rather than the first type semiconductor layer by using the conductivity of the metal substrate, and thus the fabrication thereof. The process is simpler, and the power generation area and efficiency are larger than the first structure. The third structure is a structure in which a portion of the non-conductive film is electrically connected to the metal substrate as shown in FIG. 9.

The present invention also provides a method of manufacturing a solar cell formed on a cubic aligned metal substrate.

Cubic aligned metal substrates according to the present invention are produced by methods of aligning metals well known in materials engineering. It is well known that when a metal having a face centered cubic (FCC) structure is cold-rolled to an appropriate thickness and heat-treated at an appropriate temperature, the cube texture is known. The cubic aligned metal substrate according to the present invention is produced by rolling a metal having a crystal structure of face centered cubic at a temperature of 95% or more at normal or low temperature and heat-processing at an appropriate temperature. The cubic aligned substrate has domains, and each domain has excellent vertical alignment as shown in FIG. 4, and the horizontal alignment is distributed within an error range of about 10 degrees (FIG. 4). This is very different from the crystal orientation arrangement of the general poly-crystal domains as shown in FIG. The domains present in the poly-crystals exist in a spatially random direction as shown in FIG. 3, but the cubic aligned domains are distributed with specific orientations. An example of a representative pole figure of such a substrate is Same as FIG.

When two domains have different directions in a semiconductor substrate, broken bonds exist between the two domains. 6 is an example of atoms on a plane with tetravalent bonds. At the interface between two domains 610 and 620 having different crystal directions, atoms 630 having five bonds and defects void 640 exist unlike other atoms. Since there are extra electrons in this region, the atoms in this region act as trap centers for trapping electrons or holes. As the number of these capture centers increases, electron-hole pairs generated by light are captured by the capture centers and recombined again, which is a major factor in reducing power generation efficiency. As can be seen in Figure 6, the larger the junction angle between the two domains, the higher the density of the capture centers, the lower the power generation efficiency. Therefore, the crystal arrangement shown in FIG. 4, which lowers the junction angle of each domain, has higher generation efficiency since it has fewer capture centers than in the case of poly-crystal in which the junction angle is randomly arranged as shown in FIG.

The cubic aligned metal substrate described above is used to obtain a cubic aligned semiconductor substrate as shown in FIG. The cubic aligned metal substrate is cold rolled a metal having a face centered cubic (FCC) structure such as Ni, Cu, or an alloy mainly composed of Ni, Cu, or the like, for example, Ni _0.98 W _0.03. Heat treatment produces a cubic aligned metal substrate. In the case of using an alloy containing Ni, Cu, Ni, or Cu as a main component, the melting point of the metal substrate is higher than 1000 degrees, and thus, a preferable temperature range is possible in a subsequent process.

A first type semiconductor layer and a second type semiconductor layer are formed on the substrate, wherein when the first type is p-type, the second type is n-type, and when the first type is n-type, Type means p type. In the case where the first type is p-type, the first type is formed by doping with p-type elements, that is, trivalent elements, such as B and Ga, and a semiconductor having a plurality of carriers, and the second type is an n-type element, that is, P , As, and the like are formed by doping, and a plurality of carriers are electrons.

The method of forming the first type and the second type semiconductor layer may be formed by doping the first type and the second type after growing the semiconductor crystal layer, or by growing the semiconductor crystal layer doped with the first type. It can then be produced by a method of growing a second type doped semiconductor crystal layer. The method of forming the type 1 and type 2 semiconductor layers uses a deposition method, and reduces defects in the semiconductor layer formed by forming at a temperature of 600 to 1000 degrees using a low-pressure chemical vapor deposition (LPCVD) method. It is another feature of the present invention to improve the power generation efficiency of a solar cell. If the deposition temperature is low, the density of the film decreases, so that the possibility of containing defects is increased. If the deposition temperature is more than 1000 degrees, the metal substrate may be melted, which is not preferable.

As the material used for the semiconductor layer, at least one selected from Si, SiGe alloy, or Ge among tetravalent elements is used. More preferably, when SiGe alloy is used alone or in combination with Si, a wide wavelength band of sunlight is used. By absorbing, it has high solar absorption rate.

An electrode included in the configuration of a solar cell according to the present invention includes a first type electrode connected to a first type semiconductor layer or a metal substrate and a second type electrode connected to a second type semiconductor layer. It is preferable to use a transparent electrode such as Indium-Tin-Oxide (ITO), Indium-Magnesium-Oxide (IMO), Indium-Zinc-Oxide (IZO), and the like. An electrode can be provided. It is preferable to coat an anti-reflection layer (ARL) on the top of the solar cell according to the present invention in order to reduce the reflection of light and increase efficiency.

The solar cell according to the present invention may further comprise a ceramic layer crystal grown on the cubic aligned metal substrate. It can be said to be a component for inducing the crystallinity of the cubic aligned metal substrate to the crystallinity of the semiconductor layer formed on the substrate. That is, the semiconductor layer serves as an auxiliary layer for overcoming the difference between the crystal constant of the metal substrate and the crystal constant of the semiconductor layer so that the semiconductor layer has a single crystal-like structure. In addition, when the semiconductor layer is directly formed on the metal substrate, the metal component of the metal substrate may diffuse into the semiconductor layer, thereby degrading semiconductor characteristics, and thus serves as a barrier to prevent the diffusion of the metal component.

The ceramic layer is CeO _2, Y _2, or a single-layer film selected from O _3, SrRuO _3, LaNiO _3, and La _0.7 Sr _0.3 MnO _3, or conductive ceramics in the single layer or multi-layer consisting of at least one element selected from among, or CeO ₂ / It is a multilayer film of yttria stabilized zirconia (YSZ) / CeO ₂ . However, the first type, if the electrode has a structure formed on a metal substrate and using the conductive ceramic membrane, preferably a SrRuO _3, LaNiO _3, and La _0.7 Sr _0.3 of the single-layer or multi-layer consisting of at least one selected from MnO ₃ Conductive ceramics are used. The SrRuO _3, LaNiO _3, and La _0.7 Sr _{0.3-conductive} ceramic is selected from MnO ₃ will there have a very close value to the Si lattice constant of 5.43, in particular, SrRuO ₃ is 5.6, LaNiO ₃ is a metal it has a 5.46 a lattice constant Forming the conductive ceramic layer on a substrate is very advantageous for growing single crystal silicon or semiconductor layers comprising single crystal silicon. In addition, when the first type electrode has a structure formed on the metal substrate, a nonconductive ceramic layer may be formed on the metal substrate, and a portion of the nonconductive ceramic layer may be electrically connected to the metal substrate. The non-conductive ceramic layer is selected from a monolayer film selected from CeO ₂ , Y ₂ O ₃ or a multilayer film of CeO ₂ / yttria stabilized zirconia (CeO ₂ ) / CeO ₂ , wherein an electrical connection between a portion of the ceramic layer and the metal substrate is performed. A portion of the non-conductive ceramic layer may be conductive by metal ion implantation or impurity doping, or a portion of the non-conductive ceramic layer may be formed of a conductive ceramic or a metal.

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

1 and 2 are schematic views of a substrate structure and a solar cell according to a first embodiment of the present invention, Figure 7 is a schematic view of a solar cell according to a second embodiment of the present invention, Figure 9 is a third embodiment of the present invention A schematic diagram of a solar cell according to an example.

5 shows a crystal alignment of the nickel metal substrate 110 manufactured by cold rolling and heat treating a nickel plate. The epitaxial growth of CeO ₂ on this metal substrate under moderate conditions yields a cubic aligned CeO ₂ layer 120 having a lattice constant of 0.541 nm and a junction angle between domains within a certain range. The Si or SiGe alloy or Ge 130 can be epitaxially grown within a limited thickness under suitable conditions, and the Si formed on the CeO _{2 is} nearly matched to the lattice constant of 0.541 nm of CeO ₂ at 0.543 nm. The crystallographic direction of the SiGe alloy has the same characteristics as the crystallographic direction of CeO ₂ . An example of fabricating a solar cell using this substrate is shown in FIG. An epitaxially grown CeO ₂ layer 220 is positioned on a cubic aligned metal substrate 210 obtained by cold rolling, and an epitaxially grown Si or SiGe alloy or Ge 230 is positioned thereon. The lower portion 230 of the Si, SiGe alloy, or Ge layer is doped with the first type, and one region 240 of the upper portion is doped with the second type. In order to form electrodes on the two regions 230 and 240, transparent electrodes 250 and 260 such as indium-tin-oxide (ITO), indium-magnesium-oxide (IMO), and indium-zinc-oxide (IZO) are provided. In order to increase the efficiency by reducing the reflection of light, it is preferable to coat an anti-reflection layer (ARL). The solar cell fabricated in this way is composed of several domains, but the junction angle between each domain is small, so that the trapping centers are present at low density between junctions, which reduces the probability of recombination of electron-holes. Has

As a second embodiment of the present invention, a preferred method of using the conductive properties of the metal substrate is shown in FIG. On the cubic aligned metal substrate 710, a single layer or multilayer conductive ceramic 720 consisting of one or more selected from SrRuO ₃ , LaNiO ₃ , La _0.7 Sr _0.3 MnO _3, and the like is epitaxially grown, and a first layer is formed on the conductive ceramic 720. The Si or SiGe alloy or Ge layer 730 doped with type 1 is epitaxially grown. The Si or SiGe alloy or Ge layer 730 doped with the second type is epitaxially grown on the Si or SiGe alloy or Ge layer 730, and the Si or Si doped with the second type A transparent electrode 750 is formed over the SiGe alloy or Ge layer 740 for use as an electrode. In addition, it is preferable to form an anti-reflection film 760 on the layer 750 to prevent reflection. The first type electrode of the solar cell may be installed by directly using the metal substrate 710 or by bonding 780 to the metal substrate 710, and the second type electrode may be installed on the transparent electrode 750. This arrangement has the advantage that the efficiency of the charge in the two semiconductor (730,740) constituting the solar cell is moved to the positive electrode (750,780) in the shortest distance to meet the capture center during the movement of the charge is reduced. In addition, since there is no need to install another electrode such as the transparent electrode 250 of FIG. In addition, the structure as described above can be manufactured through a single process from the metal substrate 710 to the transparent electrode 750, there is an advantage that can be manufactured using a small-scale device using the flexible characteristics of the metal plate.

As a third embodiment of the present invention, a preferred method of using the conductive properties of the metal substrate is shown in FIG. CeO _2, Y ₂ O _3, etc. are epitaxially grown on the cubic aligned metal substrate 910 under appropriate conditions to epitaxially grow a single or multi-layered non-conductive ceramic 920 and a part of the non-conductive film 920. Hard masking when the conductive ceramic 925 is formed by impurity doping such as B and P or by implanting metal elements such as Al or Cu, or when the non-conductive ceramic 920 layer is formed. Partly epitaxially grows into the non-conductive ceramic 920 by masking or the like, and the remaining part exposes the metal substrate, and then partially exposes the metal or conductive ceramic 925 to the exposed metal substrate by hard masking or the like. Form a layer. The Si, SiGe alloy or Ge layer 930 doped with a first type on the non-conductive film 920 and the conductive ceramic or metal 925 is epitaxially grown. The Si or SiGe alloy or Ge layer 930 doped with the second type is epitaxially grown on the Si or SiGe alloy or Ge layer 930, and the Si or doped with the second type A transparent electrode 950 is formed over the SiGe alloy or Ge layer 940 for use as an electrode. In addition, it is preferable to form an anti-reflection film 960 on the layer 950 to prevent reflection. The first type electrode of the solar cell may be installed by directly using the metal substrate 910 or by bonding 980 to the metal substrate 910, and the second type electrode may be installed on the transparent electrode 950. This arrangement has an advantage that the efficiency of the charges in the two semiconductors 930 and 940 constituting the solar cell moves to the positive electrodes 950 and 980 at the shortest distance, thereby reducing the probability of meeting the capture center during the movement of the charge. In addition, in the above structure, since the density of defects spontaneously formed between the conductive film and the silicon interface is smaller than that of the entire conductive film, the power generation efficiency can be improved. In the above structure, the density of the conductive film should be selected densely for the transport of charge, but should be selected at the minimum in view of the density of defects, so it should be selected for maximum efficiency by the two conflicting effects.

The present invention also provides a method of manufacturing a solar cell formed on a cubic aligned metal substrate. The above manufacturing method is a manufacturing method utilizing the ductility of a metal substrate, and the following two manufacturing methods are possible.

The first manufacturing method is to use a rotating cylinder,

(a) attaching a cubic aligned metal substrate to the cylinder;

(b) depositing a ceramic layer while rotating the cylinder;

(c) depositing a semiconductor layer on the ceramic layer while rotating the cylinder; And

(d) depositing a transparent electrode layer on the semiconductor layer while rotating the cylinder;

Characterized in that it comprises a.

The second manufacturing method is a manufacturing method using two reels,

(a) attaching a metal substrate derived from one reel wound with a cubic aligned metal substrate to the other reel;

(b) depositing a ceramic layer while winding the metal substrate from one reel to another reel;

depositing a semiconductor layer while winding the metal substrate after step (c) b); And

depositing a transparent electrode layer while winding the metal substrate after step (d) c);

Characterized in that it comprises a. In the first and second manufacturing methods, the semiconductor layer is preferably deposited in a temperature range of 600 to 1000 degrees using LPCVD. In addition, the first and the second, and the second method for producing a ceramic layer is required to use a conductive ceramic, preferably SrRuO _3, LaNiO _3, and La _0.7 Sr _0.3 MnO ₃ for a single-layer or multi-layer of conductive ceramics made of at least one element selected from among use.

The manufacturing method will be described in detail with reference to FIG. 8.

In the case of making a 1m long solar cell using a 1m long glass plate, conventional methods require photolithography equipment of similar size in addition to deposition and doping equipment having at least 1m length. However, in the case of using the manufacturing method according to the present invention, after the conductive substrate is formed while the metal substrate is wound around the cylindrical holder and the cylinder is rotated, the maximum length is 50 cm by forming the solar cell and the anti-reflection film in the same apparatus. It is possible to manufacture a solar cell of 1m length using one deposition equipment as follows. An example of the manufacturing apparatus using this method is shown in FIG. In the state of winding and rotating the cubic aligned metal substrate 810 on the cylinder 800, deposition of a ceramic thin film 820, deposition of a semiconductor layer 830, and deposition of an upper transparent electrode 840 using a deposition apparatus. By sequentially executing the large-area solar cell can be manufactured using a small size device. In addition, it is possible to continuously manufacture a long-length solar cell by sequentially applying the deposition using two reels (reel, 850) for the application of such a device. In addition, the fabricated solar cell has a simple structure with electrodes on both sides and is in the form of a thin film. Therefore, it is possible to replace a part of the thin film in the solar cell module in which a defect occurs during use. It has the advantage that the life of solar cell equipment is increased almost unlimitedly.

In addition, most solar cells do not fully absorb the sun's radiant energy, and the unabsorbed radiant energy is converted into thermal energy by heating the solar cell. This thermal energy causes a decrease in the efficiency of the solar cell. In the solar cell of the present invention, most of the thermal energy is transferred to a metal substrate having a much higher thermal conductivity than a Si substrate or a glass plate, and a cooling water is flowed into the lower portion of the metal substrate to increase the temperature. Can be prevented from falling. In addition, the cooling water under the metal substrate may be heated by heat energy and used as hot water. Therefore, the use of a metal substrate has the advantage that both electrical and thermal energy can be used.

As described above, the solar cell according to the present invention is manufactured using a cubic aligned metal thin film, and thus its manufacturing cost is low, and the density of the capture center is significantly lower than that of an amorphous or polycrystalline substrate. When a part of the light energy that is not absorbed in the solar cell is converted into thermal energy by using a metal substrate having excellent thermal conductivity, the substrate of the solar thermal substrate is lower than when using a silicon substrate or a glass substrate having low thermal conductivity. Due to the small increase in temperature, the deterioration of the power generation characteristics of the solar cell according to the increase in temperature is small, and almost all energy can be obtained as electrical energy and thermal energy by absorbing thermal energy by installing cooling water under a metal plate. In addition, in the case of a solar cell having a multi-layer structure, since the structure has a simple lamination structure, the solar cell can be manufactured only through deposition and implantation without complicated patterning process, and thus, compared with general solar cells. Manufacturing costs can be significantly lowered.

Claims (11)

A cubic aligned metal substrate obtained by cold-rolling a metal substrate having a face-centered cubic structure; A non-conductive ceramic layer crystal grown on the metal substrate; A first type semiconductor layer and a second type semiconductor layer formed on the ceramic layer; And A transparent electrode formed on the first type semiconductor layer and the second type semiconductor layer; A solar cell formed on a cubic aligned metal substrate comprising a. The method of claim 1, And the nonconductive ceramic layer is selected from a monolayer film selected from CeO ₂ , Y ₂ O ₃ or a multilayer film of CeO ₂ / YSZ (yttria stabilized zirconia) / CeO ₂ . The method of claim 1, And the first type semiconductor layer and the second type semiconductor layer are at least one layer selected from crystal grown Si, SiGe alloy, or Ge. The method of claim 3, wherein And the first type semiconductor layer and the second type semiconductor layer are deposited at 600 to 1000 degrees by LPCVD. A cubic aligned metal substrate obtained by cold-rolling a metal substrate having a face-centered cubic structure; The metal substrate and the crystal growth in SrRuO _3, LaNiO _3, and La _{0 .7} Sr _{0 .3} ceramic layer is selected from a single-layer or multi-layer consisting of at least one selected from MnO ₃ conductive ceramics; A first type semiconductor layer and a second type semiconductor layer sequentially formed on the ceramic layer; A transparent electrode formed on the second type semiconductor layer; And An electrode formed on the metal substrate; A solar cell formed on a cubic aligned metal substrate comprising a. A cubic aligned metal substrate obtained by cold-rolling a metal substrate having a face-centered cubic structure; A non-conductive ceramic layer crystal grown on the metal substrate; A first type semiconductor layer and a second type semiconductor layer sequentially formed on the ceramic layer; A transparent electrode formed on the second type semiconductor layer; And An electrode formed on the metal substrate; And a portion of said nonconductive ceramic layer electrically connected to the metal substrate. The method of claim 6, The non-conductive ceramic layer is selected from a monolayer film selected from CeO ₂ , Y ₂ O ₃ or a multilayer film of CeO ₂ / yttria stabilized zirconia (CeO ₂ ) / CeO ₂ , wherein an electrical connection between a portion of the ceramic layer and the metal substrate is performed. Formed on a cubic aligned metal substrate to be conductive by implantation or doping to a portion of the nonconductive ceramic layer of the film, or to form a portion of the nonconductive ceramic layer with conductive ceramic or metal. Solar cells. The method according to claim 5 or 6, And the first type semiconductor layer and the second type semiconductor layer are at least one layer selected from crystal grown Si, SiGe alloy, or Ge. The method according to claim 5 or 6, And the first type semiconductor layer and the second type semiconductor layer are deposited at 600 to 1000 degrees by LPCVD. (a) attaching a cubic aligned metal substrate to the cylinder; (b) depositing a ceramic layer while rotating the cylinder; (c) depositing a semiconductor layer on the ceramic layer at 600 to 1000 degrees by LPCVD while rotating the cylinder; And (d) depositing a transparent electrode layer on the semiconductor layer while rotating the cylinder; Method for manufacturing a solar cell comprising a. (a) attaching a metal substrate derived from one reel wound with a cubic aligned metal substrate to the other reel; (b) depositing a ceramic layer while winding the metal substrate from one reel to another reel; depositing the semiconductor layer at 600 to 1000 degrees by LPCVD while winding the metal substrate after step (c) b); And depositing a transparent electrode layer while winding the metal substrate after step (d) c); Method for manufacturing a solar cell comprising a.

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