WO2024039134A1 - Perovskite solar cell comprising interace layer and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a perovskite solar cell and a manufacturing method therefor, the solar cell comprising: an electron transport layer containing tin oxide; an interface layer positioned on the electron transport layer; and a light absorption layer, which is positioned on the interface layer and contains a perovskite compound, wherein the interface layer includes a pyrophosphate compound and residue derived therefrom. During a heat treatment process for forming a perovskite light absorption layer, efficiency does not decline even during high-temperature heat treatment such that thermal instability of a perovskite solar cell is solved, and thus excellent durability is provided and stability and efficiency can be enhanced.

Description

Perovskite solar cell including an interfacial layer and method for manufacturing the same

The present invention relates to a perovskite solar cell including an interfacial layer and a method of manufacturing the same. In particular, the present invention relates to a perovskite solar cell including an interfacial layer and a heat treatment process for forming a perovskite light absorption layer. The present invention relates to a perovskite solar cell that can be heat treated even at high temperatures without deteriorating efficiency, thereby improving durability and photoelectric conversion efficiency, and a method of manufacturing the same.

As the climate crisis is accelerating due to the depletion of fossil fuels and environmental pollution caused by fossil fuels, the need for eco-friendly alternative energy is emerging, and the demand for solar cells is also increasing. Among them, low-cost perovskite solar cells, which have similar efficiency to existing silicon solar cells, are attracting attention.

Organometallic halides with a perovskite structure, also referred to as organic-inorganic perovskite compounds or organometal halide perovskite compounds, contain an organic cation (A), a metal cation (M), and a halogen anion. It is composed of (X) and is a substance represented by the chemical formula of AMX₃. Perovskite compounds have high absorbance in the visible light range and can generate sufficient charge even in thin films. In addition, electrons and holes can be effectively separated due to the high extinction coefficient and small exciton binding energy, and it can be manufactured through a low-temperature process, which is economically advantageous.

Conventionally, titanium oxide was mainly used as the electron transport layer of perovskite solar cells, but tin oxide has a wider band gap than titanium oxide, high light transmittance in visible light, high electron mobility, excellent stability, non-toxicity, and perovskite. It is attracting attention as a material for the electron transport layer of high-efficiency perovskite solar cells because it has the advantages of better energy alignment with the layer and low-temperature processing.

However, due to the nature of the low-temperature solution process, defects in the electron transport layer containing tin oxide and deterioration of the perovskite solar cell caused by the high-temperature heat treatment process conducted to alleviate surface and interface defects formed are factors in performance degradation. As a result, there is a need for research on perovskite solar cells that provide improved performance with better durability and stability.

In the present invention, during the heat treatment process for forming the perovskite light absorption layer, no defects due to deterioration phenomenon occur even at high temperatures, and heat treatment is possible even at high temperatures, thereby producing perovskite solar cells and solar cells with excellent durability, improved efficiency, and stability. The purpose is to provide a method for manufacturing a low-level solar cell.

The perovskite solar cell according to the present invention contains tin oxide as an electron transport layer, has an interface layer containing a pyrophosphate compound or a residue derived therefrom on the electron transport layer, and contains a perovskite compound. The light absorption layer is located on the interface layer.

In the perovskite solar cell according to the present invention, the pyrophosphate compound may have the composition of Formula 1.

[Formula 1]

P(=O)(OR)₂-O-P(=O)(OR)₂

In Formula 1, R is independently selected from alkali metal and hydrogen, and at least one R is an alkali metal.

In the perovskite solar cell according to an embodiment of the present invention, the pyrophosphate compound may have the composition of Formula 2 below.

[Formula 2]

P(=O)(OK)₂-O-P(=O)(OK)₂

In the perovskite solar cell according to an embodiment of the present invention, the X-ray photoelectron spectroscopy (XPS) spectrum of the interface layer may include a peak of phosphorus (P) detected at a binding energy of 185 eV to 190 eV. there is.

In the perovskite solar cell according to an embodiment of the present invention, the phosphorus (P) content in the interface layer may be 0.5 to 1.2 atomic%.

In the perovskite solar cell according to an embodiment of the present invention, the thickness of the interfacial layer may be less than 5 nm.

A perovskite solar cell according to an embodiment of the present invention can satisfy Equation 1 below.

[Equation 1]

PCE ₁ /PCE ₀ > 1.4

In Equation 1, PCE ₁ is the photoelectric conversion efficiency of the perovskite solar cell including the interface layer, and PCE ₀ refers to the photoelectric conversion efficiency of the perovskite solar cell not including the interface layer.

A perovskite solar cell according to an embodiment of the present invention can satisfy Equation 2 below in the linear attenuation section of time-resolved fluorescence spectroscopy (TCSPC, time-correlated single photon counting).

[Equation 2]

τ ₁ /τ ₀ > 7.0

In Equation 2, τ ₁ refers to the carrier life of a perovskite solar cell including an interface layer, and τ ₀ refers to the carrier life of a perovskite solar cell not including an interface layer.

In the perovskite solar cell according to an embodiment of the present invention, the perovskite compound may have an AMX₃ composition, A may be a monovalent cation, M may be a divalent cation, and X may be a halide anion.

The perovskite solar cell according to the present invention includes a hole transport layer located on top of the light absorption layer; A first electrode connected to the lower part of the electron transport layer; and a second electrode connected to the top of the hole transport layer.

The present invention includes a method for manufacturing the above-described perovskite solar cell.

The method of manufacturing a perovskite solar cell according to the present invention includes forming an interface layer containing a pyrophosphate compound or a residue derived therefrom on an electron transport layer containing tin oxide; Forming a first material layer by applying and drying a perovskite precursor solution on the interface layer; and heat-treating the first material layer to form a perovskite light absorption layer.

In the method of manufacturing a perovskite solar cell according to an embodiment of the present invention, the heat treatment temperature of the first material layer may be 130°C or higher.

In the method of manufacturing a perovskite solar cell according to an embodiment of the present invention, the method of manufacturing an interface layer includes applying a solution containing a pyrophosphate compound on the electron transport layer; and heat treatment.

In the perovskite solar cell according to the present invention, an interfacial layer containing a pyrophosphate compound or a residue derived therefrom is located at the interface between an electron transport layer containing tin oxide and a light absorption layer containing a perovskite compound. During the heat treatment process to form the perovskite light absorption layer, the thermal instability of the perovskite solar cell can be resolved by increasing the heat treatment temperature without reducing efficiency, resulting in excellent durability and improved stability and efficiency.

Figure 1 is a diagram showing a current density-voltage graph according to the heat treatment temperature of the first material layer when manufacturing a perovskite solar cell according to Comparative Example 2.

Figure 2 is a diagram showing a current density-voltage graph of perovskite solar cells manufactured according to Example 1, Comparative Example 1, and Comparative Example 2.

Figure 3 shows the open-circuit voltage (V _OC ), short-circuit current density (J _SC ), fill factor (FF), and photoelectric conversion efficiency of perovskite solar cells manufactured according to Example 1, Comparative Example 1, and Comparative Example 2 ( This is a diagram showing PCE).

Figure 4 is a graph showing changes in time-correlated single photon counting (TCSPC) of perovskite solar cells manufactured according to Example 1, Comparative Example 1, and Comparative Example 2.

Figure 5 is a diagram showing the XPS analysis spectrum of the interfacial layer in the perovskite solar cell manufactured according to Example 1 and Comparative Example 2.

A perovskite solar cell providing an interfacial layer containing a pyrophosphate compound or a residue derived therefrom according to the present invention and a method for manufacturing the same will be described in detail. The terms used in this specification are general terms that are currently widely used as much as possible while considering the function of the present invention, but this may vary depending on the intention or precedent of a technician working in the related field, the emergence of new technology, etc. Unless otherwise defined, the technical and scientific terms used may have meanings commonly understood by those skilled in the art in the technical field to which this invention belongs.

Specific details for implementing the present invention will be described in detail with reference to the attached drawings. However, in the following description, detailed descriptions of well-known functions or configurations will be omitted if there is a risk of unnecessarily obscuring the gist of the present invention.

As used in this specification and the appended claims, singular expressions include plural expressions, unless the context clearly dictates the singular. Additionally, plural expressions include singular expressions, unless the context clearly specifies plural expressions.

In this specification and the appended claims, terms such as first and second are used not in a limiting sense but for the purpose of distinguishing one component from another component.

In this specification and the appended patent claims, terms such as “include” or “have” mean the presence of features or components described in the specification, and, unless specifically limited, one or more other features or This does not preclude the possibility of additional components.

In addition, the numerical range used in this specification includes the lower limit and upper limit and all values within the range, increments logically derived from the shape and width of the defined range, all double-defined values, and the upper limit of the numerical range defined in different forms. and all possible combinations of the lower bounds. Unless otherwise specified in the specification of the present invention, values outside the numerical range that may occur due to experimental error or rounding of values are also included in the defined numerical range.

In this specification and the appended patent claims, when a part of a film (layer), region, component, etc. is said to be on or on another part, it is not only a case where it is directly on top of another part in contact with another part, but also when there is another film (layer) in the middle. ), also includes cases where other areas, other components, etc. are involved.

The terms "about" and the like used in this specification and the appended claims are used to encompass tolerance when tolerance exists.

In this specification and the appended patent claims, when efficiency is simply described without any additional explanation, the efficiency refers to photoelectric conversion efficiency (Power Conversion Efficiency, PCE).

The present invention provides a perovskite solar cell, wherein the perovskite solar cell includes an electron transport layer containing tin oxide; An interface layer located on the electron transport layer; A light absorption layer located on the interface layer and containing a perovskite compound, wherein the interface layer includes a pyrophosphate compound or a residue derived therefrom.

The perovskite compound of the light absorption layer refers to an organic metal halide with a perovskite structure. Typically, perovskite compounds can satisfy the chemical formula of AMX ₃ based on monovalent organic cations (A), divalent metal cations (M), and halogen anions (X), but AMX ₄ , A ₂ MX ₄ , A ₃ Examples that satisfy chemical formulas such as MX ₅ are not excluded. In addition, perovskite compounds can have _a three-dimensional structure in which A combines with ₁₂ That is not the case.

In one embodiment, the perovskite compound satisfies the formula AMX ₃ , wherein A is a monovalent organic cation, M is a divalent metal ion, and X is selected from I ^- , Br ^- , F ^- and Cl ^- There may be one or two or more types. Examples of M, a divalent metal ion, include Cu ²⁺ , Ni ²⁺ , Co ²⁺ , Fe ²⁺ , Mn ²⁺ , Cr ²⁺ , Pd ²⁺ , Cd ²⁺ , Ge ²⁺ , Sn ²⁺ , Pb One or two or more types selected from ²⁺ and Yb ²⁺ may be mentioned, but are not limited thereto. A may be an amidinium group ion, an organic ammonium ion, or an amidinium group ion and an organic ammonium ion. Specifically, A may be represented by the formula of (R ₁ -NH ₃ ⁺ )X, where R ₁ is C1-C24 alkyl, C3-C20 cycloalkyl, or C6 ^- C20 aryl, and It means one or more halogen anions selected from Br ^- , F ^- and I ^- . In addition, A may be represented by the formula (R ₂ -C ₃ H ₃ N ₂ ⁺ -R ₃ )X, where R ₂ is C1-C24 alkyl, C3-C20 cycloalkyl, or C6-C20 aryl. , R ₃ is hydrogen or C1-C24 alkyl, and X means one or more halogen anions selected from Cl ^- , Br ^- , F ^- and I ^- . As a non-limiting and specific example, R ₁ may be C1-C24 alkyl, preferably C1-C7 alkyl, and more preferably methyl. R ₂ may be C1-C24 alkyl, R ₃ may be hydrogen or C1-C24 alkyl, preferably R ₂ may be C1-C7 alkyl and R ₃ may be hydrogen or C1-C7 alkyl, , more preferably, R ₂ may be methyl and R ₃ may be hydrogen. As a specific and non-limiting example, amidinium-based ions include formamidinium (NH ₂ CH=NH ₂ ⁺ ) ion and acetamidinium (NH ₂ C(CH ₃ )=NH ₂ ⁺ ). Or Guamidinium (NH ₂ C(NH ₂ )=NH ₂ ⁺ ), etc. may be mentioned. If A is a monovalent organic ion that contains both organic ammonium ions and amidinium ions, A is A´ _1-x A˝ _x (A˝ is the monovalent organic ammonium ion described above, and A´ is It is an amidinium-based ion, and x can satisfy the real number 0<x<1, preferably a real number 0.05≤x≤0.3).

The tin oxide of the electron transport layer may be tin oxide (SnO₂), and the thickness of the thin film may be 10 nm to 500 nm, but the present invention is not limited by the thickness of the electron transport layer.

In general, a perovskite solar cell is manufactured by forming an electron transport layer containing tin oxide and then forming a light absorption layer containing a perovskite compound, followed by heat treatment. Heat treatment at a high temperature of 130℃ or higher is preferred to suppress defects in the light absorption layer and improve PCE. However, when heat treatment is performed at a high temperature of 130℃ or higher, defects such as oxygen vacancies are generated at the interface between the electron transport layer and the light absorption layer. It acts as a trap to confine charges and does not prevent holes from moving toward the electron transport layer, causing recombination of electrons and holes. Accordingly, an electron transport layer containing tin oxide is formed, and then a perovskite precursor solution is applied and dried to form a light absorption layer, and then heat treatment is performed at a low temperature of 100°C or lower. However, as described above, the low-temperature heat treatment process inevitably causes defects in the light absorption layer, which may lead to a decrease in PCE performance.

However, by further including an interface layer containing a pyrophosphate compound or a residue derived therefrom between the electron transport layer and the light absorption layer, heat treatment at a high temperature of 130°C or higher becomes possible. Despite this high temperature heat treatment, the electron transport layer is attached to the interface layer. It can suppress the creation of defects such as oxygen vacancies, effectively suppress the recombination of electrons and holes, and provide the effect of improving durability.

Specifically, the pyrophosphate compound included in the interface layer may be represented by the following formula (1).

[Formula 1]

P(=O)(OR)₂-O-P(=O)(OR)₂

In Formula 1, R is independently selected from alkali metal and hydrogen, and at least one R is an alkali metal. Specifically, the alkali metal may be one or more selected from the group including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). It may be potassium (K).

The pyrophosphate compound is included in the interface layer between the electron transport layer and the light absorption layer, and as subsequent heat treatment is performed, the structure of the pyrophosphate compound is not maintained in the interface layer, but is converted to the form of a residue derived from the pyrophosphate compound. It can exist. The residue derived from the pyrophosphate compound essentially includes phosphorus (P), but may optionally have a structure in which oxygen (O) or an oxygen-containing ligand (OR) is covalently bonded to phosphorus.

The interface layer has a clear interface between the electron transport layer and the light absorption layer and may not necessarily exist. In an exemplary embodiment, at least a portion of the pyrophosphate compound penetrates into the interface between the electron transport layer and the light absorption layer, so that the pyrophosphate compound or a residue derived therefrom has the highest concentration in the interface layer, and the electron transport layer in the interface layer And the light absorption layer may be a layer that exists with a concentration gradient in the form of a concentration decrease due to mutual diffusion as the distance in each direction increases. In another exemplary embodiment, the pyrophosphate compound penetrates both the electron transport layer and the light absorption layer, so that the interface layer in which only the pyrophosphate compound exists is substantially absent, and the pyrophosphate compound penetrates into both the electron transport layer and the light absorption layer at a certain depth of the electron transport layer and the light absorption layer in the thickness direction. It may be a layer in which a pyrophosphate compound exists with a concentration gradient. However, in all exemplary embodiments, this does not mean that the pyrophosphate compound of the interfacial layer or a residue derived therefrom penetrates into the entire volume of the electron transport layer and the light absorption layer, and does not mean that the thickness direction of the entire volume of each layer of the electron transport layer and the light absorption layer This means that it penetrates only through a portion of the thickness and has a concentration gradient due to mutual diffusion.

According to one embodiment, the pyrophosphate compound may be represented by the following formula (2).

[Formula 2]

P(=O)(OK)₂-O-P(=O)(OK)₂

As the pyrophosphate compound is selected as the potassium pyrophosphate salt represented by Formula 2, the generation of defects such as oxygen vacancies can be effectively suppressed and the photoelectric conversion efficiency can be further improved through high temperature heat treatment of 130°C or higher.

According to one embodiment, the X-ray photoelectron spectroscopy (XPS) spectrum of the interface layer may include a peak of phosphorus (P) detected at a binding energy of 185 eV to 190 eV. Specifically, a peak for 2S phosphorus (P) can be detected at about 188 eV.

According to one embodiment, the content of phosphorus (P) in the interface layer may be 0.5 atomic% to 1.2 atomic%, specifically 0.6 atomic% to 1.1 atomic%, and more specifically 0.7 atomic% to 1.0 atomic%. Alternatively, it may be 0.5 atomic% or more, 0.6 atomic% or more, or 0.7 atomic% or more, and the upper limit may be 1.2 atomic% or less, 1.1 atomic% or less, 1.0 atomic% or less, and 0.9 atomic% or less, and may be substantially 0.8 atomic%. You can. By analyzing the materials and element concentrations contained in the interface layer through X-ray photoelectron spectroscopy (XPS), it can be confirmed that the interface layer containing phosphorus (P) was formed with a concentration gradient.

According to one embodiment, the thickness of the interfacial layer may be less than 5 nm, specifically less than 3 nm, and more specifically less than 1 nm, and may exist with a concentration gradient at a partial thickness without substantially having a clear interface. As the thickness of the interface layer satisfies the above range, it effectively contributes to the suppression of defect generation, and the pyrophosphate compound of the interface layer or residues derived therefrom do not excessively penetrate into the entire volume of the electron transport layer and light absorption layer, thereby preventing photoelectric energy. This can be particularly advantageous in terms of conversion efficiency.

According to one embodiment, the following equation 1 may be satisfied.

[Equation 1]

PCE ₁ /PCE ₀ > 1.4

In Equation 1, PCE ₁ is the photoelectric conversion efficiency of the perovskite solar cell including the interface layer, and PCE ₀ refers to the photoelectric conversion efficiency of the perovskite solar cell not including the interface layer. Advantageously PCE ₁ /PCE ₀ may be at least 1.5, at least 1.6, at least 1.7 or at least 1.8, and without limitation, at most 2.0.

Specifically, compared to the case where an electron transport layer containing tin oxide is formed, a perovskite precursor solution is applied and dried without including an interface layer to form a light absorption layer, and then heat treated at 150°C, pyrophosphate When an interface layer containing is further included and heat treated at 150° C., both open-circuit voltage and fill factor are improved, and photoelectric conversion efficiency can be significantly improved.

According to one embodiment, Equation 2 below can be satisfied in the linear attenuation section of time-correlated single photon counting (TCSPC).

[Equation 2]

τ ₁ /τ ₀ > 7.0

In Equation 2, τ ₁ refers to the carrier life of a perovskite solar cell including an interface layer, and τ ₀ refers to the carrier life of a perovskite solar cell not including an interface layer.

At this time, the time-resolved fluorescence spectral characteristics (TCSPC, Time-correlated single photon counting) of the perovskite solar cell can be measured by Edinburgh Instruments, FL920, and the sample was excited at 470 nm and the PL decay was at 800 nm. It was detected. Carrier lifetime (τ) refers to a value calculated by measuring the slope of the attenuation section through a mono-exponential fit based on time-resolved fluorescence spectral characteristics.

According to one embodiment, the carrier life of the perovskite solar cell according to the present invention may be 2000 nsec or more, specifically 2500 nsec or more, or 2800 nsec or more, and may be indefinitely 3000 nsec or less.

This means that defects at the interface between the light absorption layer and the electron transport layer are suppressed due to the interfacial layer containing the pyrophosphate compound or a residue derived therefrom, thereby reducing defects that act as charge traps. Accordingly, it is possible to effectively prevent holes photo-excited in the light absorption layer from moving to the electron transport layer, thereby inhibiting non-radiative recombination of holes and electrons at the interface between the light absorption layer and the electron transport layer, and recombining holes and electrons. As the time is delayed, electrons and holes increase, providing improved carrier lifespan and performance.

The perovskite solar cell according to the present invention may further include a hole transport layer on top of the light absorption layer, and may further include a first electrode below the electron transport layer and a second electrode on top of the hole transport layer. That is, the perovskite solar cell according to one embodiment includes a first electrode; An electron transport layer located on the first electrode; An interfacial layer located on the electron transport layer; A light absorption layer located on the interface layer; A hole transport layer located on the light absorption layer; And it may include a second electrode located on the hole transport layer.

The first electrode may be a transparent conductive electrode that is ohmic bonded to the electron transport layer. As a specific example, the materials of the transparent conductive electrode include fluorine-doped tin oxide (FTO), indium-doped tin oxide (ITO), ZnO, carbon nanotube, and graphene. ) and complexes thereof may be any one or two or more selected from the group, but are not limited thereto.

At this time, of course, a transparent substrate (support) that is a rigid substrate (support) or a flexible substrate (support) may be located below the first electrode. An example of a transparent substrate is polyethylene terephthalate (PET). ), polyethylene naphthalate (PEN), polyimide (PI), polycarbonate (PC), polypropylene (PP), triacetylcellulose (TAC), or polyethersulfone (PES) substrate, etc., but the present invention is applicable to the substrate. It is not limited to concrete materials.

The hole transport layer may be an organic hole transport layer, and the organic hole transport material of the organic hole transport layer may be a single molecule or a high molecule organic hole transport material.

Non-limiting examples of single to low molecule organic hole transport materials include pentacene, 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( One or more substances selected from cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid)-ruthenium(II)) may be included, but are not limited thereto.

It is preferable that the organic hole transport material is a polymer (hole conductive polymer), which not only ensures stable operation of the solar cell, but also allows for improved power generation efficiency through energy matching with the light absorber. Specifically, the hole-conducting polymer may include one or a combination of two or more selected from the group consisting of thiophene-based polymers, paraphenylenevinylene-based polymers, carbazole-based polymers, and triphenylamine-based polymers, and thiophene-based polymers or Triphenylamine-based polymers are preferred, and more preferably, triphenylamine-based polymers may be used. Non-limiting examples of polymeric organic hole transport materials include P3HT (poly[3-hexylthiophene]), MDMO-PPV (poly[2-methoxy-5-(3',7'- dimethyloctyloxyl)]-1,4-phenylene vinylene), MEH-PPV(poly[2-methoxy -5-(2''-ethylhexyloxy)-p-phenylene vinylene]), P3OT(poly(3-octylthiophene)), POT(poly(octylthiophene)), P3DT( poly(3-decyl thiophene)), P3DDT(poly(3-dodecyl thiophene)), PPV(poly(p-phenylene vinylene)), TFB(poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl) )diphenylamine)), Polyaniline, Spiro-MeOTAD([2,22′,7,77′-tetrkis (N,N-di-p-methoxyphenyl amine)-9,9,9′-spirobifluorine]), PCPDTBTPoly[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) benzo([1,2-b:4,5-b']dithiophene)-2,6-diyl )-alt-((5-octylthieno[3,4-c]pyrrole-4,6-dione)-1,3-diyl)), 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]), PSBTBT(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]), 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-co-benzothiadiazole), PEDOT (poly(3,4-ethylenedioxythiophene)), PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), PTAA ( One or more materials may be selected from poly(triarylamine)), poly(4-butylphenyl-diphenyl-amine), and copolymers thereof.

As a non-limiting and specific example, the hole transporter may be a thin film of an organic hole transport material, and the thickness of the thin film may be 10 nm to 500 nm, but the present invention is not limited thereto.

The hole transport layer is TBP (tertiary butyl pyridine), LiTFSI (Lithium Bis(Trifluoro methanesulfonyl)Imide), HTFSI (bis(trifluoromethane)sulfonimide), 2,6-lutidine, and Tris(2-(1H -pyrazol-1-yl)pyridine. ) Of course, it may further contain known additives such as cobalt(III).

The second electrode may be a conductive electrode that is ohmic bonded to the hole transporter, and any material commonly used as the electrode material for the front or back electrode in solar cells can be used. As a non-limiting example, when the second electrode is the electrode material of the back electrode, the second electrode is one of gold, silver, platinum, palladium, copper, aluminum, carbon, cobalt sulfide, copper sulfide, nickel oxide, and composites thereof. It may be any material selected above. As a non-limiting example, if the second electrode is a transparent electrode, the material of the second electrode may be fluorine-doped tin oxide (FTO), indium-doped tin oxide (ITO), ZnO, or CNT. It may be an inorganic conductive electrode such as (carbon nanotube) or graphene, or it may be an organic conductive material such as PEDOT:PSS.

In detailing the manufacturing method of a perovskite solar cell, the materials, structures, shapes, and sizes of the first electrode, second electrode, electron transport layer, light absorption layer, interface layer, and hole transport layer are the perovskite described above. As it is the same or similar to the solar cell, the manufacturing method of the perovskite solar cell according to the present invention includes all the contents previously described for the perovskite solar cell.

The method for manufacturing a perovskite solar cell according to the present invention includes forming an interface layer containing a pyrophosphate compound or a residue derived therefrom on an electron transport layer containing tin oxide; Forming a first material layer by applying and drying a perovskite precursor solution on the interface layer; and heat-treating the first material layer to form a perovskite light absorption layer.

Methods for forming an electron transport layer containing tin oxide include spin coating, bar coating, gravure coating, blade coating and roll coating, spray coating, chemical solution growth method, slot-die coating, chemical solution deposition method, atomic layer deposition method, and thermal evaporation method. , may be performed by one or more selected from the group including electron beam evaporation, magnetron sputtering, and pulse laser deposition.

Without limitation, it may be manufactured by applying a solution containing a tin oxide precursor onto the first electrode and heat treating it. Precursors such as tin salt (SnCl₂, SnCl₄) or tin hydrate (SnCl₂·2H₂O, SnCl₄·5H₂O) or tin nanoparticles are dissolved in a polar solvent such as deionized water, ethanol, or isopropanol for spin coating, bar coating, gravure coating, and blade. The electron transport layer can be formed by applying a tin oxide precursor solution using coating, roll coating, spray coating, and slot-die coating methods and heat treating it.

According to one embodiment, an electron transport layer containing tin oxide can be manufactured by chemical bath deposition (CBD). The solution used in CBD to deposit tin oxide is one from the group containing a tin precursor in deionized water and urea, mercaptoic acid, and hydrochloric acid, which act as a binder and stabilizer, respectively. It can be prepared by adding a specific acid selected above. An electron transport layer containing tin oxide may be formed through a chemical reaction by immersing the first electrode in the prepared solution.

After depositing a compound containing tin oxide selected from one or more of tetrakis dimethylamino Tin (TDMASn) and DBDTA ((CH₃CO₂)₂Sn[(CH₂)₃CH₃]₂) by atomic layer deposition under argon gas and oxygen or ozone gas, 120 The electron transport layer can be manufactured by heat treatment below ℃.

A thermal evaporation method in which liquid or solid tin is evaporated under high vacuum and a high temperature of 1630°C or higher and deposited on the first electrode, and a high-voltage electron beam is irradiated to a tin oxide target to deposit the evaporated tin oxide on the first electrode. Electron beam evaporation, magnetron sputtering, which deposits tin and oxygen atoms released by colliding high-energy particles into a target and irradiating a laser pulse to the target, causes the emitted gaseous tin and oxygen particles to deposit on the substrate and oxidize them. The tin oxide electron transport layer can be manufactured by one or more methods selected from the pulse laser deposition method for forming a tin thin film, but the present invention is not limited by the method of manufacturing the electron transport layer.

After forming the tin oxide electron transport layer, a step of forming an interface layer may be performed. For the interface layer, a solution containing a pyrophosphate compound is applied on the electron transport layer by methods such as spin coating, bar coating, gravure coating, blade coating, roll coating, spray coating, chemical solution growth method, and slot-die coating, It can be manufactured by heat treatment, but the present invention is not limited by the method of applying the solution.

The light absorption layer can be manufactured by spontaneous crystallization (self-assembly) as the solvent is removed from a solution (hereinafter referred to as perovskite solution) containing the ions that make up the perovskite compound and the desired additive(s). Accordingly, the above-described perovskite compound film can be manufactured using a solution application method conventionally used to prepare perovskite compounds.

The perovskite solution contains amidinium group ions, organic ammonium ions, or monovalent organic cations containing both amidinium group ions and organic ammonium ions, Cu ²⁺ , Ni ²⁺ , and Co ²⁺ , Fe ²⁺ , Mn ²⁺ , Cr ²⁺ , Pd ²⁺ , Cd ²⁺ , Ge ²⁺ , Sn ²⁺ , Pb ²⁺ and Yb ²⁺ , one or more types of divalent metal ions selected from It can be prepared by mixing a perovskite compound containing one or more monovalent halogen anions selected from I ^- , Br ^- , F ^-, and Cl ^- with a polar organic solvent.

Optionally, the perovskite solution may contain additives commonly used to improve the film quality of the perovskite compound being produced or to improve the interface properties between the perovskite compound and other components such as electron transporters. However, it goes without saying that the present invention cannot be limited by the specific type and content of the additive.

The solvent of the perovskite solution may be a polar organic solvent in which the ion source and additives are easily dissolved and can be easily volatilized and removed when dried. For example, the solvent is gamma-butyrolactone, formamide, N,N-dimethylformamide, diformamide, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, diethylene glycol, 1-methyl-2- Pyrrolidone, N,N-dimethylacetamide, acetone, α-terpineol, β-terpineol, dihydro terpineol, 2-methoxy ethanol, acetylacetone, methanol, ethanol, propanol, butanol, It may be one or two or more selected from pentanol, hexanol, ketone, methyl isobutyl ketone, etc., but the present invention is not limited by the specific substance of the solvent.

Application of the perovskite solution can be done through inkjet printing, microcontact printing, imprinting, gravure printing, gravure-offset printing, flexography printing, offset printing, reverse offset printing, slot die coating, bar coating, blade coating, and spray coating. , dip coating, roll coating, etc., but is not limited thereto. As described above, the perovskite compound film can be manufactured using a solution application method of applying a perovskite solution, and further, solvent-non-solvent application by sequentially applying a perovskite solution and a non-solvent. It can be manufactured using this method. These solution application methods and solvent-non-solvent application methods can be performed with reference to the applicant's Korean Patent No. 10-1547877 or 10-1547870.

After applying and drying the perovskite precursor solution, a step of forming a perovskite light absorption layer by heat treating the first material layer may be further performed. The heat treatment temperature may be 130°C or higher, 135°C or higher, 140°C or higher, 145°C or higher, or 150°C or higher, and may be substantially 200°C or lower.

The hole transport layer may be formed by applying and drying a solution containing an organic hole transport material on the light absorption layer. The solvent used to form the hole transport layer may be any solvent that dissolves the organic hole transport material and does not chemically react with the perovskite compound and the materials of the electron transport layer. For example, the solvent used to form the hole transport layer may be a non-polar solvent, but is not limited thereto.

The first electrode and the second electrode may be formed through a deposition process such as physical vapor deposition or chemical vapor deposition.

(Example 1)

A glass substrate coated with fluorine-containing tin oxide (FTO; F-doped SnO₂, 8 ohms/㎠, Pilkington, hereinafter referred to as FTO substrate (first electrode)) is cut to a size of 25 x 25 mm, and then the end is partially etched. FTO was removed.

The FTO substrate was cleaned by sonication in Hellmanex solution, deionized water, acetone, and isopropyl alcohol (IPA) for 10 minutes each. CBD solution (reaction solution) was prepared by mixing 625 mg of urea, 625 μL of HCl, 12.5 μL of thioglycolic acid (TGA), and 137.5 mg of SnCl ₂ ·2H ₂ O per 50 mL of deionized water. To prevent deposition of SnO ₂ , one edge of the cleaned FTO substrate was taped with Kapton tape. The taped FTO substrate and CBD solution were loaded into a glass reaction vessel (Hellendahl staining dish, ~170 mL vessel volume) and reacted at 90°C for 4 hours to form tin oxide.

The FTO substrate on which the tin oxide layer was formed by chemical solution growth was annealed at 170°C for 60 minutes at 15-30% relative humidity, and then spin-coated with deionized water containing 10mM KCl dissolved at 3000 rpm for 30 seconds. An electron transport layer was prepared by heat treatment again at 100°C for 10 minutes.

A solution was prepared by dissolving 10 mg of potassium pyrophosphate in 1 ml of water and quantifying it. This was applied on the electron transport layer, spin-coated at 3000 rpm for 30 seconds, and then heat-treated at 100°C for 3 minutes to form an interface layer. did.

An amidinium-based perovskite compound layer was formed on the tin oxide layer using a perovskite solution on the prepared interface layer. As is known, in order to improve performance, the composition of lead iodide is excessive by about 9 mol% compared to the stoichiometric ratio (ABX ₃ standard stoichiometric ratio), and methylammonium chloride (MACl) is used to stabilize the intermediate phase and improve the orientation of the perovskite compound. ; Methylammonium Chloride) was used as an additive. In detail, the perovskite solution is a mixture of dimethylformamide and dimethyl sulfoxide in an 8:1 (V/V) ratio, 1.53M lead iodide (PbI ₂₎ , and 1.4M formamidinium aiodide. It was prepared by mixing 0.0122M (0.8 mol%) methylammonium lead bromide (MAPbBr₃; methylammonium lead bromide) with (FAI; formamidinium iodide) and 0.5M methylammonium chloride (MACl; Methylammonium Chloride). The prepared perovskite solution was spin-coated at 1000 rpm for 10 seconds, followed by 5000 rpm for 30 seconds. During spin coating, 600 μL of diethyl ether was injected at 5000 rpm for 10 seconds. After forming a perovskite compound layer by spin coating a perovskite solution, heat treatment was performed at 100°C and normal pressure for 1 hour, followed by heat treatment at 150°C and normal pressure for 4 minutes to form a light absorption layer. was formed.

Then, 50 mg of Spiro-OMeTAD, 19.5 μL of 4-tert-butylpyridine (tBP; 4-tert-butylpyridine), and 5 μL of Co(III) trifluoromethanesulfonyl imide (TFSI; trifluoromethanesulfonyl imide) were placed on the light absorption layer. ) solution (0.25M in acetonitrile), 11.5 μL of lithium-trifluoromethanesulfonylimide (Li-TFSI), and 547 μL of chlorobenzene. After preparing the hole transport layer solution, 70 μL of the hole transport layer solution was applied. A hole transport layer was formed by loading on the lovskite compound layer and spin coating at 4000 rpm for 20 seconds.

Afterwards, Au was vacuum deposited on the hole transport layer using thermal evaporation to form a second electrode of 100 nm, thereby manufacturing a perovskite solar cell.

Measurement conditions : To measure the current-voltage characteristics of the manufactured solar cell, an artificial solar device (ORIEL class A solar simulator, Newport, model 91195A) and a source-meter (source-meter, Kethley, model 2420) were used. Illumination was set to AM 1.5G and calibrated to 100 mW/cm ² using a calibrated silicon reference cell. The step voltage was 10mV and the delay time was 50ms. Measurements of time correlated single photon counting (TCSPC) were performed by Edinburgh Instruments, FL920.

(Comparative Example 1)

A perovskite solar cell containing no interface layer was manufactured in the same manner as Example 1, except that the interface layer was not formed on the electron transport layer.

(Comparative Example 2)

An interface layer was prepared in the same manner as in Example 1, except that the solution containing the pyrophosphate compound was not applied to the electron transport layer, but a solution of potassium chloride dissolved in water was applied to the electron transport layer to form the interface layer. A perovskite solar cell was manufactured.

(Comparative Example 3)

A perovskite solar cell was manufactured in the same manner as in Example 1, but without forming an interface layer on the electron transport layer, and by adding phosphoric acid when manufacturing the electron transport layer containing tin oxide. did. Specifically, 7.4 at% phosphoric acid was added to the tin oxide precursor solution (sol), spin-coated at 5000 rpm for 30 seconds, dried at 100°C for 10 minutes, and then heat treated at 180°C for 30 minutes under nitrogen to form an electron transport layer. did. Afterwards, formamidinium lead iodide (FAPbI₃) and methylammonium lead bromide (MAPbBr₃) were spin-coated at a molar ratio of 0.85:0.15 to form a light absorption layer. A perovskite solar cell containing a pyrophosphoric acid compound was manufactured by depositing an 80 nm thick silver electrode on the hole transport layer containing Spiro-OMeTAD to form a second electrode.

Table 1 shows the open-circuit voltage (V _OC ), short-circuit current density (J _SC ), fill factor (FF), and This is a summary of the photoelectric conversion efficiency (PCE).

	V OC (V)	J SC (mA/cm²)	FF(%)	PCE(%)
Example 1	1.2	24.7	80.5	23.7
Comparative Example 1	1.01	24.42	64	15.8
Comparative Example 2	1.02	24.42	74	18.5
Comparative Example 3	1.14	22.61	76.71	19.72

As can be seen in Table 1, it can be seen that the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of Example 1 are all significantly improved compared to Comparative Examples 1 and 2. By introducing the interface layer containing potassium pyrophosphate of Example 1, it is possible to provide the effect of preventing deterioration of the perovskite light-absorbing layer even when heat-treated at 150°C. In addition, it can be seen that as the heat treatment temperature increases, crystal defects in the perovskite layer are alleviated, providing a perovskite solar cell with improved stability and durability.

In the case of Comparative Example 3, which provides a perovskite solar cell doped with phosphoric acid in the tin oxide electron transport layer rather than the interface layer, the performance may be improved to some extent compared to Comparative Examples 1 and 2, but the performance of Example 1 It can be seen that the degree of improvement is not significant compared to the perovskite solar cell manufactured using this method.

Figure 1 is a diagram showing current density-voltage graphs when the heat treatment temperature of the first material layer is 100°C and 150°C when manufacturing perovskite by the method of Comparative Example 2. When the heat treatment temperature of the first material layer was 100℃, the efficiency did not decrease, showing an open circuit voltage of 1.2V. However, when the heat treatment temperature was 150℃, the open circuit voltage decreased to 1V due to a defect in the electron transport layer, indicating a decrease in efficiency. You can check it.

Figure 2 is a diagram showing a current density-voltage graph of perovskite solar cells manufactured according to Example 1, Comparative Example 1, and Comparative Example 2 when heat treatment of the first material layer is performed at 150°C. In the case where the interface layer is not included (Comparative Example 1) and when potassium chloride is included in the interface layer (Comparative Example 2), the open-circuit voltage is only about 1V, whereas when potassium pyrophosphate is included in the interface layer (Example 1 ), it can be seen that the open-circuit voltage has significantly improved to 1.2V.

Figure 3 shows the open-circuit voltage (V _OC ), short-circuit current density (J _SC ), fill factor (FF), and photoelectric conversion efficiency of perovskite solar cells prepared according to Example 1, Comparative Example 1, and Comparative Example 2 ( This is a diagram showing the characteristics of PCE measured as a box and whisker plot (center line, average; box limit, standard deviation; whisker, outlier). In Figure 3, “Ref” is a perovskite solar cell manufactured by the method of Comparative Example 1, “KCl” is a perovskite solar cell manufactured by the method of Comparative Example 2, and “KPP” is a perovskite solar cell manufactured by the method of Example 1. This refers to a perovskite solar cell manufactured by . When the interface layer was not included (Comparative Example 1), the open-circuit voltage was about 1.01V, the short-circuit current density was about 24.42mA/cm², the fill factor was about 64%, and the photoelectric conversion efficiency was about 15.8%. When potassium chloride was included in the interface layer (Comparative Example 2), the open-circuit voltage was about 1.02V, the short-circuit current density was about 24.42mA/cm², the fill factor was about 74%, and the photoelectric conversion efficiency was about 18.5%. When potassium pyrophosphate was added to the layer (Example 1), an open-circuit voltage of about 1.2V, a short-circuit current density of about 24.7mA/cm², a fill factor of about 80%, and a photoelectric conversion efficiency of about 23.7% were achieved. It can be seen that the introduction of an interface layer containing potassium pyrophosphate significantly improved performance in all aspects, including open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency.

Figure 4 is a graph showing changes in time-correlated single photon counting (TCSPC) of perovskite solar cells manufactured according to Example 1, Comparative Example 1, and Comparative Example 2, and carrier life (carrier life). Lifetime, τ) may be calculated through a mono-exponential fit based on time-resolved fluorescence spectral characteristics. As shown in Figure 4, when the interface layer is not included (Comparative Example 1), the carrier life is 366 nsec, when potassium chloride is added (Comparative Example 2), the carrier life is 150 nsec, and when potassium pyrophosphate is added (Example 1) ) It can be seen that the carrier life is significantly increased when a compound containing potassium pyrophosphate is applied to the interface layer at 2825 nsec.

Figure 5 shows an XPS analysis spectrum (blue dotted line) of the interfacial layer of the perovskite solar cell prepared according to Example 1. In the spectrum of Example 1, a peak was detected at 185 to 190 eV that was not detected in the XPS spectrum (black dotted line) of the interfacial layer of the perovskite solar cell prepared according to Comparative Example 2. Through this, it can be confirmed that an interfacial layer containing phosphorus (P) has been formed.

As described above, the present invention has been described with specific details, limited embodiments, and drawings, but these are provided only to facilitate a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention Anyone skilled in the art can make various modifications and variations from this description.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described below as well as all modifications that are equivalent or equivalent to the scope of this patent claim shall fall within the scope of the spirit of the present invention. .

Claims (13)

1. An electron transport layer containing tin oxide;

   An interface layer located on the electron transport layer; and

   It includes a light absorption layer located on the interface layer and containing a perovskite compound,

   A perovskite solar cell wherein the interfacial layer includes a pyrophosphate compound or a residue derived therefrom.
2. According to paragraph 1,

   A perovskite solar cell wherein the pyrophosphate compound is represented by the following formula (1).

   [Formula 1]

   P(=O)(OR)₂-O-P(=O)(OR)₂

   (The R is independently selected from alkali metal and hydrogen, but at least one R is an alkali metal.)
3. According to paragraph 2,

   A perovskite solar cell wherein the pyrophosphate compound is represented by the following formula (2).

   [Formula 2]

   P(=O)(OK)₂-O-P(=O)(OK)₂
4. According to paragraph 1,

   A perovskite solar cell in which the X-ray photoelectron spectroscopy (XPS) spectrum of the interface layer includes a phosphorus (P) peak detected at a binding energy of 185 eV to 190 eV.
5. According to paragraph 1,

   A perovskite solar cell in which the relative element concentration of phosphorus (P) in the interface layer is 0.5 to 1.2 atomic%.
6. According to paragraph 1,

   A perovskite solar cell wherein the thickness of the interfacial layer is less than 5 nm.
7. According to paragraph 1,

   The perovskite solar cell is a perovskite solar cell that satisfies the following equation 1.

   [Equation 1]

   PCE ₁ /PCE ₀ > 1.4

   (PCE ₁ refers to the photoelectric conversion efficiency of the perovskite solar cell including the interface layer, and PCE ₀ refers to the photoelectric conversion efficiency of the perovskite solar cell not including the interface layer.)
8. According to paragraph 1,

   On the linear attenuation section of time-resolved fluorescence spectroscopy (TCSPC, Time-correlated single photon counting), the perovskite solar cell satisfies Equation 2 below.

   [Equation 2]

   τ ₁ /τ ₀ > 7.0

   (The τ ₁ refers to the carrier life of the perovskite solar cell including the interface layer, and τ ₀ refers to the carrier life of the perovskite solar cell not including the interface layer.)
9. According to paragraph 1,

   The perovskite compound has an AMX₃ composition, A is a monovalent cation, M is a divalent cation, and X is a halide anion.
10. According to paragraph 1,

    A hole transport layer located on top of the light absorption layer;

    a first electrode connected to the lower part of the electron transport layer; and

    A perovskite solar cell further comprising a second electrode connected to the top of the hole transport layer.
11. forming an interfacial layer containing a pyrophosphate compound or a residue derived therefrom on an electron transport layer containing tin oxide;

    forming a first material layer by applying and drying a perovskite precursor solution on the interface layer; and

    A method of manufacturing a perovskite solar cell comprising: heat-treating the first material layer to form a perovskite light absorption layer.
12. According to clause 11,

    A method of manufacturing a perovskite solar cell, characterized in that the temperature is 130°C or higher during the heat treatment.
13. According to clause 11,

    When forming the interface layer, applying a solution containing a pyrophosphate compound onto the electron transport layer; and

    A method of manufacturing a perovskite solar cell comprising the step of heat treatment.

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