Perovskite solar cell and tandem solar cell comprising same

Abstract

One embodiment of the present invention provides a perovskite solar cell comprising: a substrate; a first electrode disposed on the substrate; a second electrode disposed to face the first electrode; a light absorbing layer disposed between the first electrode and the second electrode and containing a perovskite-based material; and a first electron transport layer disposed between the light absorbing layer and the second electrode, wherein the first electron transport layer has a first metal and a second metal bonded in an oxide form, and based on the thickness direction of the first electron transport layer, bonding ratios of the first metal and the second metal differ between a lower region and an upper region of the first electron transport layer.

Description

Perovskite solar cell and tandem solar cell including the same

[0001] The present invention relates to a perovskite solar cell and a tandem solar cell including the same.

[0002] To reduce global dependence on fossil fuels, research and development are actively underway on alternative and clean energy sources that are environmentally friendly and non-depletable. Among these, solar cells are semiconductor devices that directly convert light energy into electrical energy. They consist of two or more layers of light-absorbing semiconductor materials. When light is irradiated onto a semiconductor diode forming a pn junction, photons are absorbed, generating electron-hole pairs. This creates a potential difference at the junction between the two dissimilar materials, causing current to flow.

[0003] Solar cells can be broadly categorized as inorganic or organic, depending on the composition of their photoactive layers. Conventionally, most solar cells were single-crystal or polycrystalline silicon solar cells. However, due to their low efficiency, development of these materials has been largely halted.

[0004] A solar cell considered a next-generation core technology is a perovskite solar cell, which is composed of a light-absorbing layer including a perovskite compound, an electron transport layer provided on one surface of the light-absorbing layer, and a hole transport layer provided on the other surface of the light-absorbing layer.

[0005] However, perovskite compounds are weak to heat, so high-temperature processes cannot be applied to form an electron transport layer on the photoabsorbing layer, limiting the materials that can be used as electron transport layers.

[0006] Currently, a mass-producible technology is a fullerene thin film formed through thermal deposition on a perovskite photoactive layer. However, the fullerene layer alone lacks the properties to block hole transport, so an additional layer with electron transport and hole blocking properties must be formed. However, the fullerene thin film has a hydrophobic surface, making it very difficult to form an additional layer on top. Even if it is formed, the low adhesion of the interface makes it difficult to control defects that cause electrical resistance. Currently, tin oxide thin films with p-type semiconductor properties are mainly used as layers that can satisfy both electrical and physical properties. However, tin oxide formed in a low-temperature process has low crystallinity and defects such as oxygen defects, which increase resistance during electron transport, reducing the open circuit voltage (Voc) and fill factor (FF) of the solar cell.

[0007] The present invention aims to provide a perovskite solar cell and a tandem solar cell including the same, which can improve the FF (Fill Factor) value and energy conversion efficiency of a solar cell by forming an improved electron transport layer.

[0008] In order to achieve the above-described object, one embodiment of the present invention discloses a perovskite solar cell including a substrate, a first electrode disposed on the substrate, a second electrode disposed to face the first electrode, a light-absorbing layer containing a perovskite-based material disposed between the first electrode and the second electrode, and a first electron transport layer disposed between the light-absorbing layer and the second electrode, wherein the first electron transport layer comprises a first metal and a second metal bonded in the form of an oxide, and a bonding ratio of the first metal and the second metal in a lower region and an upper region of the first electron transport layer is different based on a thickness direction of the first electron transport layer.

[0009] Another embodiment of the present invention for achieving the above-described object discloses a tandem solar cell including a silicon semiconductor layer, a first electrode on the silicon semiconductor layer, a second electrode disposed to face the first electrode, a light-absorbing layer containing a perovskite series material disposed between the first electrode and the second electrode, a first electron transport layer disposed between the light-absorbing layer and the second electrode, and a metal electrode on the second electrode, wherein the first electron transport layer includes a first metal and a second metal bonded in the form of an oxide, and a bonding ratio of the first metal and the second metal in a lower region and an upper region of the first electron transport layer is different based on a thickness direction of the first electron transport layer.

[0010] A perovskite solar cell and a tandem solar cell including the same according to an embodiment of the present invention can improve the FF (Fill Factor) value and energy conversion efficiency by forming the electron transport layer of the perovskite solar cell to include a multi-metal oxide and having a gradual gradient in the ratio of the multi-metal oxide.

[0011] FIG. 1 is a cross-sectional view schematically illustrating an example of a perovskite solar cell according to one embodiment of the present invention.

[0012] Figure 2 is an enlarged view of E in Figure 1.

[0013] FIG. 3 is a schematic diagram illustrating another example of the perovskite solar cell of FIG. 1.

[0014] FIG. 4 is a cross-sectional view schematically illustrating an example of a tandem solar cell including a perovskite solar cell according to one embodiment of the present invention.

[0015] Figure 5 is an enlarged view of T in Figure 4.

[0016] In order to achieve the above-described object, one embodiment of the present invention discloses a perovskite solar cell including a substrate, a first electrode disposed on the substrate, a second electrode disposed to face the first electrode, a light-absorbing layer containing a perovskite-based material disposed between the first electrode and the second electrode, and a first electron transport layer disposed between the light-absorbing layer and the second electrode, wherein the first electron transport layer comprises a first metal and a second metal bonded in the form of an oxide, and a bonding ratio of the first metal and the second metal in a lower region and an upper region of the first electron transport layer is different based on a thickness direction of the first electron transport layer.

[0017] The first electron transport layer may include a gradient thin film in which the bonding ratio of the first metal and the second metal follows the following chemical formula 1, and the bonding ratio of the first metal and the second metal gradually changes from a lower region to an upper region based on the thickness direction of the first electron transport layer.

[0018] Chemical Formula 1

[0019] M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속)

[0020] The first metal may include Sn, the second metal may include Ti, and in the first electron transport layer, the bonding ratio of Sn may decrease from a lower region to an upper region based on the thickness direction of the first electron transport layer, and the bonding ratio of Ti may increase.

[0021] The second electron transport layer further includes a fullerene series material between the first electron transport layer and the perovskite light-absorbing layer, and the fullerene series material may include PCBM or C60.

[0022] A passivation layer may further be included between the second electron transport layer and the perovskite light-absorbing layer, and the passivation layer may include LiF.

[0023] The thickness of the first electron transport layer may be 5 nm to 20 nm.

[0024] Another embodiment of the present invention for achieving the above-described object discloses a tandem solar cell including a silicon semiconductor layer, a first electrode on the silicon semiconductor layer, a second electrode disposed to face the first electrode, a light-absorbing layer containing a perovskite series material disposed between the first electrode and the second electrode, a first electron transport layer disposed between the light-absorbing layer and the second electrode, and a metal electrode on the second electrode, wherein the first electron transport layer includes a first metal and a second metal bonded in the form of an oxide, and a bonding ratio of the first metal and the second metal in a lower region and an upper region of the first electron transport layer is different based on a thickness direction of the first electron transport layer.

[0025] The first electron transport layer may include a gradient thin film in which the bonding ratio of the first metal and the second metal follows the following chemical formula 1, and the bonding ratio of the first metal and the second metal gradually changes from a lower region to an upper region based on the thickness direction of the first electron transport layer.

[0026] Chemical Formula 1

[0027] M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속)

[0028] The first metal may include Sn, the second metal may include Ti, and in the first electron transport layer, the bonding ratio of Sn may decrease from a lower region to an upper region, and the bonding ratio of Ti may increase.

[0029] The thickness of the first electron transport layer may be 5 nm to 20 nm.

[0030] The present invention is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, as well as the methods for achieving them, will become clearer with reference to the embodiments described in detail below, along with the drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various forms.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals and redundant descriptions thereof will be omitted.

[0032] In the examples below, the terms first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0033] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0034] In the examples below, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0035] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to what is shown.

[0036] In the following examples, the x-axis, y-axis, and z-axis are not limited to three axes on an orthogonal coordinate system, and can be interpreted in a broad sense that includes them. For example, the x-axis, y-axis, and z-axis may be orthogonal to each other, but may also refer to different directions that are not orthogonal to each other.

[0037] In some embodiments, where implementations are otherwise feasible, specific process sequences may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0038] One embodiment of the present invention relates to a perovskite solar cell, and another embodiment of the present invention relates to a tandem solar cell comprising a perovskite solar cell, and is described with reference to FIGS. 1 to 5, which schematically illustrate several examples of a perovskite solar cell and a tandem solar cell comprising a perovskite solar cell.

[0039] FIG. 1 is a cross-sectional view schematically illustrating an example of a perovskite solar cell according to one embodiment of the present invention, and FIG. 2 is an enlarged view of E of FIG. 1.

[0040] Referring to FIGS. 1 and 2, a perovskite solar cell may include a substrate (10), a first electrode (20) on the substrate (10), a hole transport layer (30) on the first electrode (20), a light absorption layer (40) on the hole transport layer (30), a passivation layer (50) on the light absorption layer (40), an electron transport layer (60) on the passivation layer (50), a transparent electrode (70) on the electron transport layer (60), an antireflection film (80) on the transparent electrode (70), and a second electrode (90).

[0041] Meanwhile, the perovskite solar cell according to an embodiment of the present invention illustrated in FIG. 1 relates to the pin planar structure among the four structures of general perovskite solar cells, namely, the nip mesoscopic structure, the nip planar structure, the pin planar structure, and the pin mesoscopic structure.

[0042] However, the structure of the perovskite solar cell illustrated in FIG. 1 is not limited to one embodiment, and the configuration of the electron transport layer made of a sloped thin film according to the embodiment of the present invention can be equally applied to a modified perovskite solar cell having a different structure, a different stacking order, or a different configuration.

[0043] The substrate (10) can be placed on the bottom surface to form a perovskite solar cell (1), and can include any one selected from borosilicate glass, quartz glass, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polycarbonate (PC), polypropylene (PP), triacetyl cellulose (TAC), or polyether sulfone (PES), but is not limited thereto.

[0044] The first electrode (20) can be formed on the substrate (10) and can be formed of a conductive material having light-transmitting properties.

[0045] For example, the first electrode (20) may include a transparent conductive oxide, a carbonaceous conductive material, a metallic material, etc. As the transparent conductive oxide, for example, ITO (Indium Tin Oxide), ICO (Indium Cerium Oxide), IWO (Indium Tungsten Oxide), ZITO (Zinc Indium Tin Oxide), ZIO (Zinc Indium Oxide), ZTO (Zinc Tin Oxide), GITO (Gallium Indium Tin Oxide), GIO (Gallium Indium Oxide), GZO (Gallium Zinc Oxide), AZO (Aluminum doped Zinc Oxide), FTO (Fluorine Tin Oxide), ZnO, etc. may be used. As a carbonaceous conductive material, for example, graphene or carbon nanotubes can be used, and as a metallic material, for example, metal (Ag) nanowires, multilayer metal thin films such as Au / Ag / Cu / Mg / Mo / Ti can be used. The term “transparent” in this specification refers to being able to transmit light to a certain degree or more, and is not necessarily interpreted to mean complete transparency. The materials described above are not necessarily limited to the embodiments described above, and may be formed of various materials, and the structure may also be modified in various ways, such as being a single layer or a multilayer.

[0046] The hole transport layer (30) may be formed on the first electrode (20) and may be a layer through which holes formed in the perovskite light-absorbing layer (40) described later are transferred. For example, the hole transport layer (30) may include at least one selected from among tungsten oxide (WOx), molybdenum oxide (MoOx), vanadium oxide (V2O5), and nickel oxide (NiOx), and may also include at least one selected from the group consisting of a single-molecule hole transport material and a polymer hole transport material, but is not limited thereto, and any material used in the relevant industry may be used. For example, spiro-MeOTAD [2,2',7,7'-tetrakis(N,Np-dimethoxy-phenylamino)-9,9'-spirobifluorene] can be used as the single-molecule hole transport material, and P3HT [poly(3-hexylthiophene)], PTAA (polytriarylamine), poly(3,4-ethylenedioxythiophene) or polystyrene sulfonate (PEDOT:PSS) can be used as the polymer hole transport material, but is not limited thereto.

[0047] Meanwhile, the hole transport layer (30) may further include a doping material. For example, the doping material may be a dopant selected from the group consisting of Li-series dopants, Co-series dopants, Cu-series dopants, Cs-series dopants, and combinations thereof, but is not limited thereto.

[0048] A light-absorbing layer (40) containing a perovskite-based material can be formed on a hole transport layer (30), and, for example, can play a role in allowing hole-electron pairs generated by receiving light energy from the sun to be separated into electrons or holes. At this time, electrons formed in the perovskite light-absorbing layer (40) are transferred to the electron transport layer (60) described below, and holes formed in the perovskite light-absorbing layer (40) can be transferred to the hole transport layer (30).

[0049] For example, the perovskite light-absorbing layer (40) may have a structure represented by the chemical formula ABX3 (wherein A may be a monovalent organic cation or metal cation, B may be a divalent metal cation, and X may be a halogen anion).

[0050] As a specific example, the perovskite light-absorbing layer (40) may include an organic halide perovskite such as methyl ammonium iodide (MAI), formamidinium iodide (FAI), or a metal halide perovskite such as lead iodide (PbI2), bromine iodide (PbBr), and lead chloride (PbCl2), and may be a multilayer stacked structure including at least one of the organic halide perovskite or the metal halide perovskite. More specifically, the perovskite light-absorbing layer (40) may include CH3NH3PbI3, CH3NH3PbI x Cl 3-x , CH3NH3PbI x Br 3-x , CH3NH3PbCl x Br 3-x , HC(NH2)2PbI3, HC(NH2)2PbI x Cl 3-x , HC(NH2)2PbI x Br 3-x , HC(NH2)2PbCl x Br 3-x , (CH3NH3)(HC(NH2)2) 1-y PbI3, (CH3NH3)(HC(NH2)2) 1-y PbI x Cl 3-x , (CH3NH3)(HC(NH2)2) 1-y PbI x Br 3-x , or (CH3NH3)(HC(NH2)2) 1-y PbCl x Br 3-x It can include (0≤x, y≤1).

[0051] The façade layer (50) can be formed on the perovskite light-absorbing layer (40), and for example, can serve to prevent the metal oxide forming the electron transport layer (60) described below from oxidizing the perovskite compound forming the light-absorbing layer.

[0052] As an optional embodiment, the payback layer (50) may include LiF.

[0053] The electron transport layer (60) may be formed on the perovskite light-absorbing layer (40), and according to an embodiment of the present invention, may include a first electron transport layer (61) formed by combining a first metal (M1) and a second metal (M2) in the form of an oxide, and a second electron transport layer (62) formed of a fluorene series material.

[0054] The first electron transport layer (61) can be formed as in the following chemical formula 1, and can be a gradient thin film in which the first metal (M1) and the second metal (M2) are combined in the form of an oxide, and the combination ratio of the first metal (M1) and the second metal (M2) gradually changes from the lower region (A) to the upper region (B) based on the thickness direction of the first electron transport layer (61).

[0055]

[0056] [Chemical Formula 1]

[0057] M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속)

[0058]

[0059] Specifically, the first electron transport layer (61) may be formed by combining a first metal and a second metal in the form of an oxide with a certain combination ratio, and the combination ratio of the first metal may gradually decrease or increase from the lower region (A) to the upper region (B), and as the combination ratio of the first metal gradually decreases, the combination ratio of the second metal gradually increases, and as the combination ratio of the first metal gradually increases, the combination ratio of the second metal gradually decreases, and may be a sloped thin film. At this time, the combination ratio of the first metal and the second metal may selectively vary depending on the material of the second electron transport layer (62) and the upper transparent electrode (70) described below.

[0060] Meanwhile, in the embodiment of the present invention, a metal oxide containing two different metals is described as an example as a material constituting the first electron transport layer (61), but it is not limited thereto and a metal oxide containing three or more metals may also be used, and the oxidation number of the metal oxide may also be selectively changed depending on the metal.

[0061] The first electron transport layer (61) may include at least one selected from SnOx, TiOx, ZnOx, WOx, NbOx, InOx, AlOx, HfOx BaSnOx, ZrOx, VOx, and CeOx, and may be formed by atomic layer deposition (ALD).

[0062] Meanwhile, in order to form the first electron transport layer (61) as a gradient thin film, atomic layer deposition (ALD) can be used, and by simultaneously injecting different metal sources that can react with each other into the same chamber while adjusting the ratio according to the ratio to be formed, the first electron transport layer (61) can be formed as a gradient thin film.

[0063] Meanwhile, the first electron transport layer (61) may be formed with a thickness of 5 nm to 20 nm. In this case, if formed with a thickness thinner than 5 nm, the hole blocking characteristics may be reduced, and if formed with a thickness thicker than 20 nm, the electron transport characteristics may be reduced, so that the performance of the perovskite solar cell (1) element may be reduced.

[0064] As an optional embodiment, the first metal may include tin (Sn), and the second metal may include titanium (Ti). In this case, the lower region (A) of the first electron transport layer (61) in contact with the second electron transport layer (62) may be formed so that the binding ratio of tin (Sn) is higher than that of titanium (Ti), and as it goes toward the upper region (B), the binding ratio of tin (Sn) may gradually decrease, and the binding ratio of titanium (Ti) may gradually increase.

[0065] In this way, when the ratio of tin (Sn) is formed high in the lower region (A) of the first electron transport layer (61), it can exhibit excellent adhesion properties with the second electron transport layer (62) formed of a fullerene series material having hydrophobicity, and the thin film process can be performed at a relatively low temperature, so that the second electron transport layer (62) formed of a fullerene series material that is weak to heat can be prevented from being damaged by heat, and further, the light absorption layer formed of a perovskite compound that is weak to heat can be prevented from being damaged by heat, thereby reducing the performance of the solar cell device.

[0066] In addition, as the bonding ratio of tin (Sn) gradually decreases and the bonding ratio of titanium (Ti) gradually increases toward the upper region (B) of the first electron transport layer (61), the energy band matching of the first electron transport layer (61) can be improved, and oxygen defects that may occur in tin (Sn) oxide can be improved.

[0067] RatioDevice ParameterSnTiVoc(V)Jsc(mA / cm 2)FF(%)PEC(%)1.001.71418.7368.3921.960.90.11.75118.7172.0623.610.70.31. 76418.7378.2025.830.50.51.75418.7076.3325.030.30.71.71518.7569.5322.37

[0068] Table 1 shows the parameters of the solar cell device according to the combination ratio of tin (Sn) and titanium (Ti) forming the first electron transport layer (61). Referring to Table 1, when the ratio of tin (Sn) is 1.0 and the ratio of titanium (Ti) is 0, it can be confirmed that the open circuit voltage (Voc) of the solar cell device is 1.714 V and the fill factor (FF) is 68.39%. Afterwards, when the ratio of tin (Sn) becomes 0.7 and the ratio of titanium (Ti) becomes 0.3, it can be confirmed that the open circuit voltage (Voc) and the fill factor (FF) gradually increase to 1.764 V and 78.20%, respectively.

[0069] That is, as the binding ratio of tin (Sn) gradually decreases and the binding ratio of titanium (Ti) gradually increases toward the upper region (B) of the first electron transport layer (61), the energy band matching of the first electron transport layer (61) is improved, so that the open circuit voltage (Voc) of the solar cell element increases, and oxygen defects that may occur in the tin (Sn) oxide are improved, so that the filling factor (FF) of the solar cell element increases.

[0070] The transparent electrode (70) can be formed of a conductive material having light transmittance on the electron transport layer (60), and may include, for example, a transparent conductive oxide, a carbonaceous conductive material, a metallic material, etc. As the transparent conductive oxide, for example, ITO (Indium Tin Oxide), ICO (Indium Cerium Oxide), IWO (Indium Tungsten Oxide), ZITO (Zinc Indium Tin Oxide), ZIO (Zinc Indium Oxide), ZTO (Zinc Tin Oxide), GITO (Gallium Indium Tin Oxide), GIO (Gallium Indium Oxide), GZO (Gallium Zinc Oxide), AZO (Aluminum doped Zinc Oxide), FTO (Fluorine Tin Oxide), ZnO, etc. can be used. As a carbonaceous conductive material, for example, graphene or carbon nanotubes can be used, and as a metallic material, for example, metal (Ag) nanowires, multilayer metal thin films such as Au / Ag / Cu / Mg / Mo / Ti can be used. The term “transparent” in this specification refers to being able to transmit light to a certain degree or more, and is not necessarily interpreted to mean complete transparency. The materials described above are not necessarily limited to the embodiments described above, and may be formed of various materials, and the structure may also be modified in various ways, such as being a single layer or a multilayer.

[0071] An anti-reflection film (80) can be formed on a transparent electrode (70), and can play a role in preventing sunlight irradiated onto a perovskite solar cell (1) from being reflected, thereby improving the transmittance of sunlight and increasing the efficiency of the perovskite solar cell (1).

[0072] For example, the antireflection film (80) may include fluorine (F) having high light transmittance and very low refractive index, and may optionally include LiF.

[0073] The second electrode (90) can be formed on the transparent electrode (80) and can serve to electrically connect the perovskite solar cell (1) to the outside.

[0074] For example, the second electrode (90) may be formed of a metal material such as silver (Ag), and a pattern of a certain shape may be formed to allow sunlight to enter the inside of the cell.

[0075] FIG. 3 is a cross-sectional view schematically illustrating another example of the perovskite solar cell of FIG. 1.

[0076] Referring to FIG. 3, the aforementioned perovskite solar cell (1) can have at least some layers textured to improve light efficiency. By texturing at least some layers of the perovskite solar cell in this way, an uneven surface is formed in the direction in which light is incident, and the light scattering effect of the light incident through the uneven surface increases the path of light incident on the perovskite light-absorbing layer (40), thereby improving light capture and thus increasing the absorption rate of sunlight.

[0077] As a result, the perovskite solar cell according to the embodiment of the present invention can exhibit excellent adhesion properties with the second electron transport layer formed of a fullerene-based material having hydrophobicity by forming the first electron transport layer as a gradient thin film, and the thin film process can be performed at a relatively low temperature, thereby preventing the fullerene-based material and the perovskite compound, which are weak to heat, from being damaged by heat, thereby reducing the performance of the perovskite solar cell device.

[0078] In addition, the open circuit voltage (Voc) and fill factor (FF) of the perovskite solar cell can be increased by improving the energy band matching and oxygen defects of the first electron transport layer.

[0079] FIG. 4 is a cross-sectional view schematically illustrating an example of a tandem solar cell including a perovskite solar cell according to one embodiment of the present invention, and FIG. 5 is an enlarged view of T of FIG. 4.

[0080] Referring to FIGS. 4 and 5, a tandem solar cell (2) including a perovskite solar cell may include a silicon semiconductor layer (100), a first electrode (200) formed on the silicon semiconductor layer (100), a hole transport layer (300) formed on the first electrode (200), a perovskite light-absorbing layer (400) formed on the hole transport layer (300), an electron transport layer (500) formed on the perovskite light-absorbing layer (400), a transparent electrode (700) formed on the electron transport layer (500), an antireflection film (800) formed on the transparent electrode (700), and a second electrode (900).

[0081] Meanwhile, a tandem solar cell (2) including a perovskite solar cell may include a silicon solar cell (lower cell) (1000) and a perovskite solar cell (upper cell) (2000) formed on the silicon solar cell (1000), and a bonding layer (not shown) may be provided between the silicon solar cell (1000) and the perovskite solar cell (2000) to bond and electrically connect the two. This bonding layer may be implemented using a transparent conductive oxide (TCO), a carbonaceous conductive material, a metallic material, or a conductive polymer so that long-wavelength light passing through the perovskite solar cell (2000) may be incident on the silicon solar cell (1000) disposed thereunder without transmission loss.

[0082] The silicon solar cell (1000) may be a silicon solar cell having a band gap of around 1.0 eV to 1.2 eV. It may include a back electrode (not shown) made of a metal or metal alloy disposed on the substrate, and a silicon semiconductor layer (100) disposed on the back electrode. At this time, the back electrode may include silver (Ag), titanium (Ti), gold (Au), or the like.

[0083] The silicon semiconductor layer (100) may include a p-type silicon semiconductor layer and an n-type silicon semiconductor layer disposed on the p-type silicon semiconductor layer.

[0084] A perovskite solar cell (2000) may include a first electrode (200), a hole transport layer (300), a light absorption layer (400) containing a perovskite series material, an electron transport layer (500), a transparent electrode (700), an antireflection film (800), and a second electrode (900).

[0085] The first electrode (200) may be formed of a conductive material having light-transmitting properties, and may include, for example, a transparent conductive oxide, a carbonaceous conductive material, a metallic material, etc. As the transparent conductive oxide, for example, ITO (Indium Tin Oxide), ICO (Indium Cerium Oxide), IWO (Indium Tungsten Oxide), ZITO (Zinc Indium Tin Oxide), ZIO (Zinc Indium Oxide), ZTO (Zinc Tin Oxide), GITO (Gallium Indium Tin Oxide), GIO (Gallium Indium Oxide), GZO (Gallium Zinc Oxide), AZO (Aluminum doped Zinc Oxide), FTO (Fluorine Tin Oxide), ZnO, etc. may be used. As a carbonaceous conductive material, for example, graphene or carbon nanotubes can be used, and as a metallic material, for example, metal (Ag) nanowires, multilayer metal thin films such as Au / Ag / Cu / Mg / Mo / Ti can be used. The term “transparent” in this specification refers to being able to transmit light to a certain degree or more, and is not necessarily interpreted to mean complete transparency. The materials described above are not necessarily limited to the embodiments described above, and may be formed of various materials, and the structure may also be modified in various ways, such as being a single layer or a multilayer.

[0086] The hole transport layer (300) may be formed on a silicon solar cell (1000) and may be a layer through which holes formed in the perovskite light-absorbing layer (400) described later are transported. For example, the hole transport layer (300) may include at least one selected from among tungsten oxide (WOx), molybdenum oxide (MoOx), vanadium oxide (V2O5), and nickel oxide (NiOx), and may also include at least one selected from the group consisting of a single-molecule hole transport material and a polymer hole transport material, but is not limited thereto, and any material used in the relevant industry may be used. For example, spiro-MeOTAD [2,2',7,7'-tetrakis(N,Np-dimethoxy-phenylamino)-9,9'-spirobifluorene] can be used as the single-molecule hole transport material, and P3HT [poly(3-hexylthiophene)], PTAA (polytriarylamine), poly(3,4-ethylenedioxythiophene) or polystyrene sulfonate (PEDOT:PSS) can be used as the polymer hole transport material, but is not limited thereto.

[0087] Meanwhile, the hole transport layer (300) may further include a doping material. For example, the doping material may be a dopant selected from the group consisting of Li-series dopants, Co-series dopants, Cu-series dopants, Cs-series dopants, and combinations thereof, but is not limited thereto.

[0088] The light-absorbing layer (400) containing a perovskite series material can be formed on the hole transport layer (300), and for example, can play a role in allowing hole-electron pairs generated by receiving light energy from the sun to be separated into electrons or holes. At this time, electrons formed in the perovskite light-absorbing layer (400) are transferred to the electron transport layer (500) described below, and holes formed in the perovskite light-absorbing layer (400) can be transferred to the hole transport layer (300).

[0089] For example, the perovskite light-absorbing layer (400) may have a structure represented by the chemical formula ABX3 (wherein A may be a monovalent organic cation or metal cation, B may be a divalent metal cation, and X may be a halogen anion).

[0090] As a specific example, the perovskite light-absorbing layer (400) may include an organic halide perovskite such as methyl ammonium iodide (MAI), formamidinium iodide (FAI), or a metal halide perovskite such as lead iodide (PbI2), bromine iodide (PbBr), and lead chloride (PbCl2), and may be a multilayer stacked structure including at least one of the organic halide perovskite or the metal halide perovskite. More specifically, the perovskite light-absorbing layer (400) may include CH3NH3PbI3, CH3NH3PbI x Cl 3-x , CH3NH3PbI x Br 3-x , CH3NH3PbCl x Br 3-x , HC(NH2)2PbI3, HC(NH2)2PbI x Cl 3-x , HC(NH2)2PbI x Br 3-x , HC(NH2)2PbCl x Br 3-x , (CH3NH3)(HC(NH2)2) 1-yPbI3, (CH3NH3)(HC(NH2)2) 1-y PbI x Cl 3-x , (CH3NH3)(HC(NH2)2) 1-y PbI x Br 3-x , or (CH3NH3)(HC(NH2)2) 1-y PbCl x Br 3-x It can include (0≤x, y≤1).

[0091] The electron transport layer (500) may be formed on the perovskite light-absorbing layer (400), and according to an embodiment of the present invention, may include a first electron transport layer (510) formed by combining a first metal (M1) and a second metal (M2) in the form of an oxide, and a second electron transport layer (520) formed of a fluorene series material.

[0092] The first electron transport layer (510) may be formed as in the following chemical formula 1, and may be a gradient thin film in which the first metal (M1) and the second metal (M2) are combined in the form of an oxide, and the combination ratio of the first metal (M1) and the second metal (M2) gradually changes from the lower region (A) to the upper region (B).

[0093]

[0094] [Chemical Formula 1]

[0095] M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속)

[0096]

[0097] Specifically, the first electron transport layer (510) may be formed by combining a first metal and a second metal in the form of an oxide with a certain combination ratio, and the combination ratio of the first metal may gradually decrease or increase from the bottom (A) to the top (B) based on the thickness direction of the first electron transport layer (51), and as the combination ratio of the first metal gradually decreases, the combination ratio of the second metal gradually increases, and as the combination ratio of the first metal gradually increases, the combination ratio of the second metal gradually decreases, so that it may be a sloped thin film. At this time, the combination ratio of the first metal and the second metal may selectively vary depending on the material of the second electron transport layer (520) and the upper transparent electrode (600) described below.

[0098] Meanwhile, in the embodiment of the present invention, a metal oxide containing two different metals is described as an example as a material constituting the first electron transport layer (510), but it is not limited thereto and a metal oxide containing three or more metals may also be used, and the oxidation number of the metal oxide may also be selectively changed depending on the metal.

[0099] The first electron transport layer (510) may include at least one selected from SnOx, TiOx, ZnOx, WOx, NbOx, InOx, AlOx, HfOx BaSnOx, ZrOx, VOx, and CeOx, and may be formed by atomic layer deposition (ALD).

[0100] Meanwhile, in order to form the first electron transport layer (51) as a gradient thin film, atomic layer deposition (ALD) can be used, and by simultaneously injecting different metal sources that can react with each other into the same chamber while adjusting the ratio according to the ratio to be formed, the first electron transport layer (510) can be formed as a gradient thin film.

[0101] Meanwhile, the first electron transport layer (510) may be formed with a thickness of 5 nm to 20 nm. In this case, if formed with a thickness thinner than 5 nm, the hole blocking characteristics may be reduced, and if formed with a thickness thicker than 20 nm, the electron transport characteristics may be reduced, so that the performance of the perovskite solar cell (2000) element may be reduced.

[0102] As an optional embodiment, the first metal may include tin (Sn), and the second metal may include titanium (Ti). In this case, the lower region (A) of the first electron transport layer (510) in contact with the second electron transport layer (520) may be formed so that the binding ratio of tin (Sn) is higher than that of titanium (Ti), and as it goes toward the upper region (B), the binding ratio of tin (Sn) may gradually decrease, and the binding ratio of titanium (Ti) may gradually increase.

[0103] In this way, when the ratio of tin (Sn) is formed high in the lower region (A) of the first electron transport layer (510), it can exhibit excellent adhesion properties with the second electron transport layer (520) formed of a fullerene series material having hydrophobicity, and the thin film process can be performed at a relatively low temperature, so that the second electron transport layer (520) formed of a fullerene series material that is weak to heat can be prevented from being damaged by heat, and further, the light absorption layer formed of a perovskite compound that is weak to heat can be prevented from being damaged by heat, thereby reducing the performance of the solar cell device.

[0104] In addition, as the bonding ratio of tin (Sn) gradually decreases and the bonding ratio of titanium (Ti) gradually increases toward the upper region (B) of the first electron transport layer (510), the energy band matching of the first electron transport layer (510) can be improved, and oxygen defects that may occur in tin (Sn) oxide can be improved.

[0105] RatioDevice ParameterSnTiVoc(V)Jsc(mA / cm 2)FF(%)PEC(%)1.001.71418.7368.3921.960.90.11.75118.7172.0623.610.70.31. 76418.7378.2025.830.50.51.75418.7076.3325.030.30.71.71518.7569.5322.37

[0106] Table 2 shows the parameters of the solar cell device according to the combination ratio of tin (Sn) and titanium (Ti) forming the first electron transport layer (510). Referring to Table 1, when the ratio of tin (Sn) is 1.0 and the ratio of titanium (Ti) is 0, it can be confirmed that the open circuit voltage (Voc) of the solar cell device is 1.714 V and the fill factor (FF) is 68.39%. Afterwards, when the ratio of tin (Sn) becomes 0.7 and the ratio of titanium (Ti) becomes 0.3, it can be confirmed that the open circuit voltage (Voc) and the fill factor (FF) gradually increase to 1.764 V and 78.20%, respectively.

[0107] That is, as the binding ratio of tin (Sn) gradually decreases and the binding ratio of titanium (Ti) gradually increases toward the upper region (B) of the first electron transport layer (510), the energy band matching of the first electron transport layer (510) is improved, so that the open circuit voltage (Voc) of the solar cell element increases, and oxygen defects that may occur in the tin (Sn) oxide are improved, so that the filling factor (FF) of the solar cell element increases.

[0108] As an optional embodiment, a façade layer (not shown) may be formed between the perovskite light-absorbing layer (400) and the electron transport layer (500). For example, the façade layer (not shown) may serve to prevent the metal oxide forming the electron transport layer (500) from oxidizing the perovskite compound forming the light-absorbing layer (400).

[0109] As an optional embodiment, the payback layer may comprise LiF.

[0110] The transparent electrode (600) can be formed of a conductive material having light transmittance on the electron transport layer (500), and may include, for example, a transparent conductive oxide, a carbonaceous conductive material, a metallic material, etc. As the transparent conductive oxide, for example, ITO (Indium Tin Oxide), ICO (Indium Cerium Oxide), IWO (Indium Tungsten Oxide), ZITO (Zinc Indium Tin Oxide), ZIO (Zinc Indium Oxide), ZTO (Zinc Tin Oxide), GITO (Gallium Indium Tin Oxide), GIO (Gallium Indium Oxide), GZO (Gallium Zinc Oxide), AZO (Aluminum doped Zinc Oxide), FTO (Fluorine Tin Oxide), ZnO, etc. can be used. As a carbonaceous conductive material, for example, graphene or carbon nanotubes can be used, and as a metallic material, for example, metal (Ag) nanowires, multilayer metal thin films such as Au / Ag / Cu / Mg / Mo / Ti can be used. The term “transparent” in this specification refers to being able to transmit light to a certain degree or more, and is not necessarily interpreted to mean complete transparency. The materials described above are not necessarily limited to the embodiments described above, and may be formed of various materials, and the structure may also be modified in various ways, such as being a single layer or a multilayer.

[0111] An anti-reflection film (700) can be formed on a transparent electrode (600), and can play a role in preventing sunlight irradiated onto a perovskite solar cell (2000) from being reflected, thereby improving the transmittance of sunlight and increasing the efficiency of the perovskite solar cell (1).

[0112] For example, the antireflection film (700) may include a fluorine (F) material having high light transmittance and very low refractive index, and may optionally include LiF.

[0113] The second electrode (800) can be formed on the transparent electrode (700) and can serve to electrically connect the perovskite solar cell (2000) to the outside.

[0114] For example, the second electrode (800) may be formed of a metal material such as silver (Ag) and may be formed in a grid pattern to allow sunlight to enter the inside of the cell.

[0115] As a result, the perovskite solar cell according to the embodiment of the present invention and the tandem solar cell including the same can exhibit excellent adhesion properties with the second electron transport layer formed of a fullerene-based material having hydrophobicity by forming the first electron transport layer as a gradient thin film, and the thin film process can be performed at a relatively low temperature, thereby preventing the fullerene-based material and the perovskite compound, which are weak to heat, from being damaged by heat, thereby reducing the performance of the perovskite solar cell device.

[0116] In addition, the open circuit voltage (Voc) and fill factor (FF) of the perovskite solar cell can be increased by improving the energy band matching and oxygen defects of the first electron transport layer.

[0117] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

[0118] The specific implementations described in the embodiments are exemplary embodiments and do not limit the scope of the embodiments in any way. For the sake of brevity of the specification, descriptions of conventional electronic components, control provision methods, software, and other functional aspects of the above provision methods may be omitted. In addition, the lines connecting or connecting members between components illustrated in the drawings are merely representative of functional connections and / or physical or circuit connections, and may be replaced or represented as various additional functional connections, physical connections, or circuit connections in an actual device. In addition, if there is no specific mention such as “essential,” “important,” etc., the component may not be absolutely necessary for the application of the present invention.

[0119] The use of the term "above" and similar referential terms in the specification of embodiments (especially in the claims) may refer to both singular and plural. Furthermore, if a range is described in the embodiments, the invention encompasses individual values ​​within the range (unless otherwise stated), and is equivalent to describing each individual value constituting the range in the detailed description. Finally, unless the order of steps constituting a method according to an embodiment is explicitly stated or otherwise stated to the contrary, the steps may be performed in any suitable order. The embodiments are not necessarily limited by the order in which the steps are described. The use of all examples or exemplary terms (e.g., "for example," etc.) in the embodiments is merely intended to describe the embodiments in detail, and the scope of the embodiments is not limited by the examples or exemplary terms, unless otherwise defined by the claims. Furthermore, those skilled in the art will recognize that various modifications, combinations, and variations may be made within the scope of the appended claims or their equivalents, depending on design conditions and factors.

Claims

1. Substrate; A first electrode disposed on the substrate; A second electrode positioned to face the first electrode; A light-absorbing layer containing a perovskite series material disposed between the first electrode and the second electrode; and A first electron transport layer disposed between the light absorbing layer and the second electrode, A perovskite solar cell, wherein the first electron transport layer comprises a first metal and a second metal combined in the form of an oxide, and the bonding ratios of the first metal and the second metal in a lower region and an upper region of the first electron transport layer are different based on the thickness direction of the first electron transport layer.

2. In paragraph 1, A perovskite solar cell, wherein the first electron transport layer is a gradient thin film in which the bonding ratio of the first metal and the second metal follows the following chemical formula 1, and the bonding ratio of the first metal and the second metal gradually changes from a lower region to an upper region based on the thickness direction of the first electron transport layer. Chemical Formula 1 M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속) 3. In paragraph 2, The first metal includes Sn, the second metal includes Ti, A perovskite solar cell, wherein the first electron transport layer has a binding ratio of Sn decreasing and a binding ratio of Ti increasing from a lower region to an upper region based on the thickness direction of the first electron transport layer.

4. In paragraph 1, Further comprising a second electron transport layer comprising a fullerene series material between the first electron transport layer and the perovskite light absorbing layer, The above fullerene series material is a perovskite solar cell containing PCBM or C60.

5. In paragraph 4, Further comprising a passivation layer between the second electron transport layer and the perovskite light absorbing layer, A perovskite solar cell, wherein the passivation layer comprises LiF.

6. In paragraph 1, A perovskite solar cell, wherein the thickness of the first electron transport layer is 5 nm to 20 nm.

7. Silicon semiconductor layer; A first electrode on the silicon semiconductor layer; A second electrode positioned to face the first electrode; A light-absorbing layer containing a perovskite series material disposed between the first electrode and the second electrode; a first electron transport layer disposed between the light absorbing layer and the second electrode; and Including a metal electrode on the second electrode, A tandem solar cell, wherein the first electron transport layer comprises a first metal and a second metal combined in the form of an oxide, and the bonding ratios of the first metal and the second metal in a lower region and an upper region of the first electron transport layer are different based on the thickness direction of the first electron transport layer.

8. In paragraph 7, A tandem solar cell, wherein the first electron transport layer is a gradient thin film in which the bonding ratio of the first metal and the second metal follows the following chemical formula 1, and the bonding ratio of the first metal and the second metal gradually changes from a lower region to an upper region based on the thickness direction of the first electron transport layer. Chemical Formula 1 M1 (1-x) M2 x O2(0 <X<1, M1: 제1 금속, M2: 제2 금속) 9. In paragraph 8, The first metal includes Sn, the second metal includes Ti, A tandem solar cell, wherein the first electron transport layer has a binding ratio of Sn decreasing from a lower region to an upper region, and a binding ratio of Ti increasing.

10. In paragraph 7, A tandem solar cell, wherein the thickness of the first electron transport layer is 5 nm to 20 nm.

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