KR20230159925A - Tandem solar cell and manufacturing method thereof - Google Patents

Abstract

A tandem solar cell according to an embodiment of the present invention includes a lower cell; A perovskite upper cell disposed on the lower cell; A bonding layer connecting the lower cell and the perovskite upper cell between the lower cell and the perovskite upper cell, wherein the bonding layer is a first transparent electrode layer disposed in contact with the lower cell, It may include a buffer layer disposed on the first transparent electrode layer and a second transparent electrode layer disposed on the buffer layer and in contact with the upper cell.

Description

Tandem solar cell and manufacturing method thereof}

The present invention relates to tandem solar cells and methods for manufacturing the same.

Solar cells are eco-friendly devices that convert solar energy into electricity. Solar power generation is possible only when sunlight is absorbed by the light absorption layer of a solar cell and electron-hole pairs are formed. Only incident light greater than the band gap of the light absorption layer is absorbed, and among that, the extra energy is equal to the difference between the energy of the incident light and the band gap. is consumed as heat energy, and the energy of incident light below the band gap is not absorbed. Therefore, in order to efficiently use sunlight, tandem solar cells incorporating multiple light absorption layers with different band gaps are attracting attention.

Perovskite, which is in the spotlight as a light absorption layer material for next-generation solar cells, is easy to control the bandgap and can be used as a material for the lower part of thin-film solar cells such as silicon, copper indium gallium selenide (CIGS), and copper zinc tin sulfide (CZTS). When bonded to a cell, efficient distribution of incident light with the lower cell is possible. In addition, perovskite can form a thin film through a low-temperature solution process, thus lowering the production price.

The silicon solar cell used as the lower cell of the tandem solar cell and the upper perovskite cell are connected by a bonding layer. The bonding layer uses a transparent electrode layer such as ITO, and has a thickness of several tens of nm, so it is greatly affected by the surface condition of the lower cell.

On the other hand, the silicon solar cell has a concavo-convex structure of several micrometers (μm) on the top to reduce reflection of incident light. This greatly affects the surface properties of the bonding layer and may cause defects when forming the bonding layer. Moreover, even if a silicon solar cell without an uneven structure is used, the bonding layer may be formed unevenly due to the imbalance in the surface energy and morphology of the Si layer, causing a decrease in the performance and stability of the upper cell.

The present invention was created to overcome the above-mentioned problems, and one of the several purposes of the present invention is to improve the performance of tandem solar cells.

One of the many purposes of the present invention is to provide a tandem solar cell capable of forming a uniform bonding layer and a method for manufacturing the same.

One of the many purposes of the present invention is to provide a tandem solar cell that can improve the surface morphology of the bonding layer and a method of manufacturing the same.

One of the many purposes of the present invention is to provide a tandem solar cell and a method of manufacturing the same that can minimize the influence of surface defects of the lower cell.

One of the many purposes of the present invention is to provide a tandem solar cell and a method of manufacturing the same that can improve the stability of the combination of the upper cell and the lower cell.

A tandem solar cell according to an embodiment of the present invention includes a lower cell; A perovskite upper cell disposed on the lower cell; A bonding layer connecting the lower cell and the perovskite upper cell between the lower cell and the perovskite upper cell, wherein the bonding layer is a first transparent electrode layer disposed in contact with the lower cell, It may include a buffer layer disposed on the first transparent electrode layer and a second transparent electrode layer disposed on the buffer layer and in contact with the upper cell, and the average thickness of the buffer layer may be 1 nm or more and/or 5 nm or less. there is.

At this time, the lower cell is a silicon solar cell, perovskite solar cell, CIGS (Chalcopyrite) solar cell, CZTS (Copper zinc tin sulfide) solar cell, GaAs solar cell, InGaAs solar cell, InGaAs solar cell, and InGaP solar cell. It may be one or more selected from the group consisting of.

Additionally, the buffer layer may include one or more oxides selected from the group consisting of Sn, Hf, Al, Si, Zn, In, Ti, Ni, Mg, and alloys thereof.

Additionally, the lower cell may include an n-type doped layer.

Additionally, the buffer layer may include components different from those of the first transparent electrode layer.

Meanwhile, the first transparent electrode layer and/or the second transparent electrode layer of the tandem solar cell according to the present invention is one selected from the group consisting of ITO, IZO, AZO, FTO, metal nanowire, graphene, carbon nanotubes, and conductive polymer. It may include more.

Additionally, the average thickness of the first transparent electrode layer may be 5 nm or more and/or 10 nm or less.

Additionally, the average thickness of the second transparent electrode layer may be 10 nm or more and/or 25 nm or less.

At this time, the average thickness of the bonding layer may be 16 nm or more and/or 31 nm or less.

In one example, the first transparent electrode layer and the second transparent electrode layer may include different components.

In another embodiment according to the present invention, a method for manufacturing a tandem solar cell according to the present invention includes forming a first transparent electrode layer on a lower cell; forming a buffer layer on the first transparent electrode layer; and forming a second transparent electrode layer on the buffer layer, wherein the average thickness of the buffer layer may be 1 nm or more and/or 5 nm or less.

Additionally, the method of manufacturing a tandem solar cell according to the present invention may further include forming a perovskite upper cell on the second transparent electrode layer.

In one example of the present invention, the average thickness of the first transparent electrode layer may be 5 nm or more and/or 10 nm or less.

Additionally, the average thickness of the second transparent electrode layer may be 10 nm or more and/or 25 nm or less.

Meanwhile, according to one example of the present invention, the first transparent electrode layer and the second transparent electrode layer may include different components.

One of the many effects of the present invention is that it can improve the performance of tandem solar cells.

One of the many effects of the present invention is to provide a tandem solar cell capable of forming a uniform bonding layer and a method for manufacturing the same.

One of the many effects of the present invention is to improve the surface morphology of the bonding layer between the upper cell and the lower cell.

One of the many effects of the present invention is to minimize the influence of surface defects on the lower cell of a tandem solar cell.

One of the many effects of the present invention is to improve the stability of the combination of the upper cell and the lower cell.

1 is a cross-sectional view schematically showing a tandem solar cell according to an embodiment of the present invention.
Figure 2 is a graph showing the series resistance values of tandem solar cells manufactured in Examples and Comparative Examples of the present invention.
Figure 3 is a graph showing parallel resistance values of tandem solar cells manufactured in Examples and Comparative Examples of the present invention.
Figure 4 is a graph showing the conversion efficiency of tandem solar cells manufactured in Examples and Comparative Examples of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to specific embodiments and attached drawings. This is not intended to limit the technology described herein to specific embodiments, but should be understood to include various modifications, equivalents, and/or alternatives to the embodiments of the present invention. In connection with the description of the drawings, similar reference numbers may be used for similar components.

In order to clearly explain the present invention in the drawings, parts that are not relevant to the description are omitted, and the thickness is enlarged to clearly express various layers and regions. Components with the same function within the scope of the same idea are referred to by the same reference. It can be explained using symbols.

In this specification, terms such as “comprise” or “have” are intended to describe the existence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to describe the presence of one or more other features. It should be understood that it does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

A component being “in front,” “rear,” “above,” or “below” another component means that it is in direct contact with the other component, unless there are special circumstances. This includes not only those placed at the “bottom” but also cases where another component is placed in the middle. Additionally, when a part of a layer, membrane, region, etc. is said to be “on” or “on” another part, this includes not only cases where it is directly on top of the other part, but also cases where there is another part in between. The fact that a component is "connected" to another component includes not only being directly connected to each other, but also indirectly connected to each other, unless there are special circumstances.

As used herein, expressions such as “A and/or B,” “at least one of A and B,” or “one or more of A and B” may include all possible combinations of the items listed together. For example, “A and/or B,” “at least one of A and B,” or “one or more of A and B” means (1) includes at least one A, (2) includes at least one It may refer to all cases including B, or (3) including both at least one A and at least one B.

In the drawing, the In addition, the transport direction of the conveyor described later in this specification is the X direction, the direction perpendicular to the It can be defined as direction.

Tandem solar cell

The present invention relates to tandem solar cells. 1 is a cross-sectional view schematically showing a tandem solar cell according to an embodiment of the present invention. Referring to Figure 1, the tandem solar cell 1 according to the present invention includes a lower cell 10; A perovskite upper cell (20) disposed on the lower cell (10); And a bonding layer (30) between the lower cell (10) and the perovskite upper cell (20) that combines the lower cell (10) and the perovskite upper cell (20). there is.

At this time, the bonding layer 30 includes a first transparent electrode layer 301 disposed in contact with the lower cell 10, a buffer layer 310 disposed on the first transparent electrode layer 301, and the buffer layer 310. It may include a second transparent electrode layer 302 disposed on the upper cell 20 and in contact with the upper cell 20, and the average thickness of the buffer layer 310 may be 1 nm or more and/or 5 nm or less.

Conventional tandem solar cells used a single layer as a bonding layer connecting the lower cell and the upper cell. The bonding layer functions to electrically connect the open-circuit voltage of the upper and lower cells. It physically separates the upper and lower cells and receives electrons and holes from the upper and lower cells, respectively, to combine them. In addition, the light of the spectrum that is not absorbed in the upper cell must be transmitted to the lower cell. For this reason, the thickness must be thin, but depending on the surface condition of the lower cell, the uniformity of the crystal phase may decrease or defects may occur due to imbalance in surface energy or morphology. There are problems that arise.

The present inventors discovered that the above problem can be solved through a multi-layered bonding layer. The bonding layer according to the present invention can minimize the influence of the surface condition of the lower cell by having a structure in which a first transparent electrode layer, a buffer layer, and a second transparent electrode layer are stacked. For example, the structure may be a structure in which the interface formed by the first transparent electrode layer, the buffer layer, and the second transparent electrode layer is arranged to be parallel to each other, and the interface may be formed in a direction perpendicular to the stacking direction. It is not limited to this. In this specification, values representing angles such as vertical and parallel may be values considering an error range, and the error range may be, for example, within the range of ±1 degree, ±2 degree, ±3 degree, ±4 degree, or ±5 degree. there is. By having the above structure, the tandem solar cell according to the present invention can prevent the performance of the upper cell from being deteriorated even if a defect occurs in the first transparent electrode layer. Additionally, the alignment of energy levels can be improved by collecting different charges transmitted from the top and bottom, respectively.

In one example of the present invention, the lower cell of the tandem solar cell according to the present invention includes a silicon solar cell, a perovskite solar cell, a CIGS (Chalcopyrite) solar cell, a CZTS (Copper zinc tin sulfide) solar cell, a GaAs solar cell, It may be one or more selected from the group consisting of an InGaAs solar cell, an InGaAs solar cell, and an InGaP solar cell. In this specification, a lower cell may refer to a solar cell formed at the lower part of a tandem solar cell. For example, a silicon lower cell may refer to a case where the solar cell formed at the lower part is a silicon solar cell. In addition, in this specification, a silicon solar cell, perovskite solar cell, CIGS (Chalcopyrite) solar cell, CZTS (Copper zinc tin sulfide) solar cell, GaAs solar cell, InGaAs solar cell, InGaAs solar cell, and InGaP solar cell are respectively This may refer to a solar cell in which the light absorption layer includes silicon, perovskite compound, CIGS (Chalcopyrite), CZTS (Copper zinc tin sulfide), GaAs, InGaAs, InGaAs, and InGaP.

The lower cell may have one of the structures of known solar cells as long as it includes a light absorption layer containing the above-mentioned components, and is not limited to a specific structure. For example, if the subcell is a silicon subcell, the silicon subcell may be a crystalline silicon solar cell or an amorphous silicon solar cell, including a lower electrode layer (not shown), a p-type or n-type silicon substrate (not shown), and It may include an n-type doped layer (not shown). Additionally, the silicon lower cell may further include additional layers as needed in addition to the above-mentioned layers.

At this time, the bonding layer according to the present invention may be disposed in contact with the n-type doped layer. When the lower cell uses a p-type substrate, the n-type doped layer can function as an emitter layer, and when the lower cell uses an n-type substrate, the n-type doped layer can function as an emitter layer (FSF). It can function as a Front Surface Field. Since the bonding layer is disposed on the lower cell of the tandem solar cell according to the present invention, the lower cell may include an n-type doped layer, and the n-type doped layer located at the top of the lower cell (n-doped layer) and the bonding layer may be disposed in contact with each other.

The bonding layer of the tandem solar cell according to the present invention may include a first transparent electrode layer, a buffer layer, and a second transparent electrode layer, and may have a structure in which the layers are sequentially stacked. Since the first transparent electrode layer forms an interface in contact with the n-type doped layer (n-doped layer), it is important that the first transparent electrode layer matches the n-type doped layer (n-doped layer). Therefore, the first transparent electrode layer may include a material with excellent electron trapping ability from an n-type doped layer. In addition, since the first transparent electrode layer is formed by direct deposition on the n-type doped layer, a material capable of low-temperature deposition is used to prevent damage to the n-type doped layer. It can be included.

In one example of the present invention, the average thickness of the first transparent electrode layer may be 5 nm or more and/or 10 nm or less. If the thickness of the first transparent electrode layer is less than 5 nm, electrical performance may be reduced, and if the thickness of the first transparent electrode layer is more than 10 nm, the effectiveness of the buffer layer may be reduced.

The bonding layer of the tandem solar cell according to the present invention may include a buffer layer disposed on the first transparent electrode layer. The buffer layer can prevent physical defects on the n-doped layer of the lower cell from affecting the upper cell. In addition, the buffer layer can function as an effective recombination layer through band engineering between the first transparent electrode layer and the second transparent electrode layer, and selective mobility of carriers through the buffer layer with a wide band gap. can increase.

The buffer layer may include various components that can equalize surface energy. In addition, it has a wide band gap that facilitates tunneling and may contain a conductive material as a charge/hole transport layer for the upper and lower cells. The buffer layer may include, for example, an oxide of one or more materials selected from the group consisting of Sn, Hf, Al, Si, Zn, In, Ti, Ni, Mg, and alloys thereof.

In one example, the buffer layer of the tandem solar cell according to the present invention may include different components from the first transparent electrode layer. That the buffer layer includes a material different from the first transparent electrode layer may mean that the main component is substantially different from the first transparent electrode layer, and that the main component is substantially different means that the component that occupies the largest weight among the components of the buffer layer and This may mean that the component occupying the largest weight among the components of the first transparent electrode layer is different. As in this example, the buffer layer contains different components from the first transparent electrode layer, so even if a defect occurs in the first transparent electrode layer due to the influence of the lower cell, the buffer layer can block it, improving the electrical performance and mechanical durability of the upper cell. and can improve the electrical/optical characteristics of the entire tandem solar cell.

In another example, the average thickness of the buffer layer of the tandem solar cell according to the present invention may be 1 nm or more and/or 5 nm or less. The conventional single-layer recombination layer had a problem in that it was difficult to adjust the thickness to a thin thickness due to the surface morphology of the lower cell. In comparison, the buffer layer of the tandem solar cell according to the present invention can have a very thin thickness because the first transparent electrode layer blocks the influence of the lower cell while functioning as a recombination layer. The average thickness of the buffer layer may be 5 nm or less, less than 5 nm, 4 nm or less, 3 nm or less, and may be 1 nm or more. If the average thickness of the buffer layer is less than 1 nm, a uniform thin film may not be formed, and if it is 5 nm or more or more than 5 nm, it may hinder the movement of carriers.

The buffer layer may be a vapor deposition layer formed by vapor deposition. The deposition method of the buffer layer is not particularly limited as long as it satisfies the above-mentioned thickness and composition, but for example, chemical vapor deposition, physical vapor deposition, vacuum deposition, or atomic layer. Atomic layer deposition method can be used.

The tandem solar cell according to the present invention may include a second transparent electrode layer disposed on the buffer layer. The second transparent electrode layer may be disposed in contact with the upper cell. Since the upper cell of the tandem solar cell according to the present invention is a perovskite solar cell as will be described later, the second transparent electrode layer may include an interface in contact with the hole transport layer of the upper cell. Accordingly, the second transparent electrode layer has important compatibility with the hole transport layer of the upper cell, and may include a component formed in the upper cell that has excellent hole trapping ability.

In one example of the present invention, the average thickness of the second transparent electrode layer may be 10 nm or more and/or 25 nm or less. If the second transparent electrode layer is less than 10 nm, electrical properties may deteriorate, and if it is more than 25 nm, optical properties may be lost.

In one example, the first transparent electrode layer and the second transparent electrode layer of the tandem solar cell according to the present invention are each independently made of indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), and fluorine (FTO). doped tin oxide), metal nanowires, graphene, carbon nanotubes, and conductive polymers.

A perovskite upper cell may be disposed on the bonding layer of the tandem solar cell according to the present invention. Within this specification, an upper cell may refer to a solar cell formed on the upper part of a tandem solar cell, and a perovskite upper cell may refer to a case where the solar cell formed on the upper part is a perovskite solar cell. The perovskite upper cell may have one of the structures of known perovskite solar cells, and is not limited to a specific structure. For example, the perovskite upper cell may include a structure in which a hole transport layer (not shown), a perovskite light absorption layer (not shown), and an electron transport layer (not shown) are stacked.

The hole transport layer (HTL, or hole transport layer) may be a layer that transports holes formed in the perovskite light absorption layer and blocks the movement of electrons, and may include an inorganic and/or organic hole transport material. You can. Examples of the inorganic hole transport material include nickel oxide (NiOx), copper thiocyanate (CuSCN), CuCrO ₂ and copper iodide (CuI), but these are merely examples and are not limited thereto.

In addition, the organic hole transport material includes carbazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorene derivatives, hydrazone derivatives, stilbene derivatives, and sila. Residue derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidine compounds, porphyrin compounds, phthalocyanine compounds, polythiophene derivatives, polypyrrole derivatives, polyparaphenylenevinylene derivatives, pentacene. , Coumarin 6 (coumarin 6, 3-(2-benzothiazolyl)-7-(diethylamino)coumarin), ZnPC (zinc phthalocyanine), CuPC (copper phthalocyanine), TiOPC (titanium oxide phthalocyanine), Spiro-MeOTAD (2,2' ,7,7'-tetrakis(N,N-p-dimethoxyphenylamino)-9,9'-spirobifluorene), F16CuPC(copper(II) 1,2,3,4,8,9,10,11,15,16,17 ,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine), SubPc (boron subphthalocyanine chloride) and N3 (cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'- dicarboxylic acid)-ruthenium(II), P3HT (poly[3-hexylthiophene]), MDMO-PPV (poly[2-methoxy-5-(3',7'-dimethyloctylacyl)]-1,4-phenylene vinylene), MEH-PPV(poly[2-methoxy-5-(2''-ethylhexyloxy)-p-phenylene vinylene]), P3OT(poly(3-octyl thiophene)), POT(poly(octyl thiophene)), P3DT(poly (3-decyl thiophene)), P3DDT(poly(3-dodecyl thiophene)), PPV(poly(p-phenylene vinylene)), TFB(poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenyl) amine), Polyaniline, Spiro-MeOTAD ([2,22', 7, 77'-tetrkis (N,N-di-pmethoxyphenyl amine)-9,9,9''-spirobi fluorine]), CuSCN, CuI, PCPDTBT (Poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl-4H-cyclopenta [2,1-b:3,4-b']dithiophene-2 ,6-diyl]], Si-PCPDTBT(poly[(4,4′’-bis(2-ethylhexyl)dithieno[3,2-b:2′’,3′’-d]silole)-2,6 -diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl]), PBDTTPD(poly((4,8-diethylhexyloxyl), PFDTBT(poly[2,7-(9-(2-ethylhexyl) )-9-hexyl-fluorene)-alt-5,5-(4', 7, -di-2-thienyl-2',1', 3'-benzothiadiazole)]), PFO-DBT(poly[2, 7-.9,9-(dioctyl-fluorene)-alt-5,5-(4',7'-di-2-.thienyl-2', 1', 3'-benzothiadiazole)]), PSiFDTBT(poly [(2,7-dioctylsilafluorene)-2,7-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5'-diyl]), PCDTBT(Poly [[9-(1-octylnonyl)-9H-carbazole-2,7-diyl] -2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]), PFB (poly(9,9′’-dioctylfluorene-co-bis(N,N′’-(4,butylphenyl))bis(N,N′’-phenyl-1,4-phenylene)diamine), F8BT(poly( 9,9′’-dioctylfluorene-cobenzothiadiazole), PEDOT (poly(3,4-ethylenedioxythiophene)), PEDOT:PSS poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), PTAA (poly(triarylamine)), 2PACz(2 -(9H-Carbazol-9-yl)ethyl]phosphonic Acid), Me-4PACz(4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid) and MeO-2PACz(2-( It may include one or more selected from the group consisting of 3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic Acid), but is not limited thereto.

The perovskite light absorption layer disposed on the hole transport layer may include a general perovskite material applied to the light absorption layer of a solar cell. For example, the perovskite material may include a perovskite material represented by the following formula (1).

[Formula 1]

ABX ₃

In Formula 1, A is Formamidinium, Methylammonium, Cesium, Rubidium, Potassium, Sodium, Lithium, Guanidinium ( Guanidinum, Butylammonium, Ethylammonium, or Phenethylammonium, and B is Lead, Tin, Germanium, Cadmium, and Zinc. Or manganese (Magnesium), and (Selenocyanate), Formate or Acetate.

As an embodiment of Formula 1, FAPbI _x Br _3-x (0 ≤ x ≤ 3), MAPbI _x Br _3-x (0 ≤ x ≤ 3), Cs _1-yz MA _y FAzPbI _x Br _3-x (0 ≤ x ≤ 3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ y + z ≤ 1), CH ₃ NH ₃ PbX ₃ (X=Cl, Br, I, BrI ₂ , or Br2 _I ), CH ₃ NH ₃ SnX ₃ (X=Cl, Br or I), CH(=NH)NH ₃ PbX ₃ (X=Cl, Br, I, BrI ₂ , or Br ₂ I) or CH(=NH)NH ₃ SnX ₃ (X=Cl, Br or I), but is not limited thereto.

An electron transport layer may be disposed on the perovskite light absorption layer of the perovskite upper cell of the tandem solar cell according to the present invention. The electron transporting layer (ETL) may be a layer that transports electrons formed in the perovskite light absorption layer and blocks the movement of holes. The electron transport layer is, for example, TiO ₂ , SnO ₂ , ZnO, NiO, WO ₃ , TiSrO ₃ , BaSnO ₃ , NbOH, Nb ₂ O ₅ , graphene, carbon nanotubes, C60 (fullerene), PCBM ([ 6,6]-Phenyl-C61-butyric Acid Methyl Ester) or a combination thereof, but is not limited thereto.

An upper electrode layer (not shown) may be disposed on the electron transport layer of the perovskite upper cell of the tandem solar cell according to the present invention. In addition, the perovsachite upper cell may further include additional layers as needed in addition to the above-described layers.

Manufacturing method of tandem solar cell

The present invention also relates to a method for manufacturing tandem solar cells. The method of manufacturing a tandem solar cell according to the present invention includes forming a first transparent electrode layer on the lower cell; forming a buffer layer on the first transparent electrode layer; and forming a second transparent electrode layer on the buffer layer.

The structures and components of the lower cell, the first transparent electrode layer, the buffer layer, and the second transparent electrode layer are the same as those described above, so they will be omitted.

The method of forming the first transparent electrode layer on the lower cell is not particularly limited as long as it satisfies the characteristics of the first transparent electrode layer described above. For example, the first transparent electrode layer may be manufactured by a solution process, a vacuum method, a deposition method, or a mixing process, but is not limited thereto.

In one example of the present invention, the buffer layer in the method of manufacturing a tandem solar cell according to the present invention may be formed by deposition. Examples of the deposition method include, but are not limited to, chemical vapor deposition, physical vapor deposition, vacuum deposition, or atomic layer deposition. .

The method of forming the second transparent electrode layer on the buffer layer is not particularly limited as long as it satisfies the characteristics of the second transparent electrode layer described above. For example, the second transparent electrode layer may be manufactured by a solution process, a vacuum method, a deposition method, or a mixing process, but is not limited thereto.

The method of manufacturing a tandem solar cell according to the present invention may further include forming a perovskite upper cell on the second transparent electrode layer. Forming the perovskite upper cell may include sequentially forming a hole transport layer, a perovskite light absorption layer, and an electron transport layer. The method of forming the hole transport layer, perovskite light absorption layer, and electron transport layer is not particularly limited, and can be formed, for example, by a coating method such as spin coating or a deposition method such as sputtering.

[Example 1]

Preparation of bonding layer

A silicon solar cell was used as the bottom cell of the tandem solar cell. To remove the oxide film formed on the upper surface of the silicon solar cell, it was treated with hydrofluoric acid and the remaining hydrofluoric acid was washed using ultrapure water.

A first transparent electrode layer was formed on the surface of the cleaned lower cell by sputtering. A buffer layer was formed by atomic layer deposition of SnO ₂ on the formed first transparent electrode layer. A second transparent electrode layer was formed on the surface of the buffer layer again by sputtering to form a bonding layer.

Manufacturing of the upper cell

에서 10분동안 열처리하여 300nm 두께의 페로브스카이트 결정구조를 가지는 제1페로브스카이트 광흡수층(Cs1-y-zMAyFAzPbIxBr3-x(0 ≤ x ≤ 3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ y + z ≤ 1))을 형성하였다. 이후 형성된 상기 페로브스카이트 광흡수층 상에 전자 수송층을 형성하였다.A hole transport layer was formed on the bonding layer through vacuum deposition. After coating the hole transport layer by applying a precursor solution prepared by dissolving the perovskite material in a solvent containing dimethylformamide (DMF), 150

Heat treated for 10 minutes to produce a first perovskite light absorption layer (Cs1-y-zMAyFAzPbIxBr3-x(0 ≤ x ≤ 3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ y + z ≤ 1)) was formed. Afterwards, an electron transport layer was formed on the formed perovskite light absorption layer.

[Example 2]

The first transparent electrode layer was formed by sputtering an ITO thin film to a thickness of 5 to 10 nm, the SnO ₂ buffer layer of 1 to 2 nm was formed by atomic layer deposition, and the second transparent electrode layer was formed by sputtering an ITO thin film. A tandem solar cell was manufactured in the same manner as in Example 1, except that.

[Comparative Example 1]

A tandem solar cell was manufactured in the same manner as in Example 1, except that an ITO thin film with a single-layer structure was used as a bonding layer and as a transparent electrode layer.

[Comparative Example 2]

A tandem solar cell was manufactured in the same manner as in Example 1, except that a structure in which a first transparent electrode layer was formed as a bonding layer and a second transparent electrode layer was formed on the formed layer was applied.

Figures 2 to 4 below show graphs measuring the performance of tandem solar cells according to Examples and Comparative Examples of the present invention. 2 to 4, A shows the results of Comparative Example 1, B shows the results of Example 1, C shows the results of Example 2, and D shows the results of Comparative Example 2l.

Figure 2 shows the results of measuring the series resistance values of the tandem solar cells manufactured in Examples 1 and 2 of the present invention and the tandem solar cells of Comparative Examples 1 and 2. Referring to Figure 2, it can be seen that in Examples 1 and 2 of the present invention, the series resistance decreases over time. On the other hand, it can be seen that Comparative Examples 1 and 2 resulted in an increase in series resistance. Through this, it can be confirmed that the tandem solar cell according to the present invention exhibits excellent electrical characteristics over time due to the buffer layer being disposed between the first transparent electrode layer and the second transparent electrode layer.

Figure 3 shows the results of measuring the parallel resistance values of the tandem solar cells manufactured in Examples 1 and 2 of the present invention and the tandem solar cells of Comparative Examples 1 and 2. Referring to Figure 3, it can be seen that in Examples 1 and 2 of the present invention, the parallel resistance increases over time. In comparison, in Comparative Examples 1 and 2, it can be seen that the parallel resistance decreases. Through this, it can be confirmed that the tandem solar cell according to the embodiment of the present invention has excellent electrical characteristics over time.

Figure 4 shows the results of measuring the conversion efficiency of the tandem solar cells manufactured in Examples 1 and 2 of the present invention and the tandem solar cells of Comparative Examples 1 and 2. Referring to Figure 4, it can be seen that the hysteresis is reduced in Examples 1 and 2 of the present invention and Comparative Example 1. On the other hand, it can be seen that Comparative Example 2 resulted in increased hysteresis. Additionally, in Examples 1 and 2, it can be seen that the hysteresis reduction is very large. Through this, it can be confirmed that the tandem solar cell according to the present invention exhibits excellent hysteresis characteristics due to the buffer layer being disposed between the first transparent electrode layer and the second transparent electrode layer.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited by the above-described embodiments and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and change may be made by those skilled in the art without departing from the technical spirit of the present invention as set forth in the claims, and this also falls within the scope of the present invention. something to do.

1: Tandem solar cell
10: lower cell
20: Perovsachite upper cell
30: bonding layer
301: first transparent electrode layer
302: second transparent electrode layer

Claims (15)

lower cell;
A perovskite upper cell disposed on the lower cell;
It includes a bonding layer between the lower cell and the perovskite upper cell to join the lower cell and the perovskite upper cell,
The bonding layer includes a first transparent electrode layer disposed in contact with the lower cell,
A buffer layer disposed on the first transparent electrode layer, and
It includes a second transparent electrode layer disposed on the buffer layer and in contact with the upper cell,
A tandem solar cell wherein the buffer layer has an average thickness of 1 nm or more and/or 3 nm or less.
According to paragraph 1,
The lower cell is a group consisting of a silicon solar cell, perovskite solar cell, CIGS (Chalcopyrite) solar cell, CZTS (Copper zinc tin sulfide) solar cell, GaAs solar cell, InGaAs solar cell, InGaAs solar cell, and InGaP solar cell. One or more tandem solar cells selected from.
According to paragraph 1,
A tandem solar cell wherein the buffer layer includes an oxide of one or more elements selected from the group consisting of Sn, Hf, Al, Si, Zn, In, Ti, Ni, Mg, and alloys thereof.
According to paragraph 1,
The lower cell is a tandem solar cell including an n-type doped layer.
According to paragraph 1,
A tandem solar cell wherein the buffer layer includes a different component from the first transparent electrode layer.
According to paragraph 1,
The first transparent electrode layer and/or the second transparent electrode layer is a tandem solar cell comprising at least one selected from the group consisting of ITO, IZO, AZO, FTO, metal nanowire, graphene, carbon nanotubes, and conductive polymer.
According to paragraph 1,
A tandem solar cell wherein the average thickness of the first transparent electrode layer is 5 nm or more and/or 10 nm or less.
According to paragraph 1,
A tandem solar cell wherein the average thickness of the second transparent electrode layer is 10 nm or more and/or 25 nm or less.
According to paragraph 1,
A tandem solar cell wherein the average thickness of the bonding layer is 16 nm or more and/or 31 nm or less.
According to paragraph 1,
A tandem solar cell wherein the first transparent electrode layer and the second transparent electrode layer include different components.
Forming a first transparent electrode layer on the lower cell;
forming a buffer layer on the first transparent electrode layer; and
Comprising: forming a second transparent electrode layer on the buffer layer,
A method of manufacturing a tandem solar cell wherein the buffer layer has an average thickness of 1 nm or more and/or 5 nm or less.
According to clause 11,
A method of manufacturing a tandem solar cell further comprising forming a perovskite upper cell on the second transparent electrode layer.
According to clause 11,
A method of manufacturing a tandem solar cell wherein the average thickness of the first transparent electrode layer is 5 nm or more and/or 10 nm or less.
According to clause 11,
A method of manufacturing a tandem solar cell wherein the average thickness of the second transparent electrode layer is 10 nm or more and/or 25 nm or less.
According to clause 11,
A method of manufacturing a tandem solar cell wherein the first transparent electrode layer and the second transparent electrode layer include different components.