WO2024195914A1 - Method for preparing bis(methylcyclopentadienyl)nickel, and nickel oxide thin film using same - Google Patents

Abstract

A method for preparing bis(methylcyclopentadienyl)nickel, according to one embodiment of the present invention, does not require preparation of an anhydrous solvent, and uses a cheap and safe alkali metal hydroxide, and thus has excellent process stability. Furthermore, bis(methylcyclopentadienyl)nickel prepared by the method has excellent yield and purity. In addition, a method for manufacturing a nickel oxide thin film, according one embodiment of the present invention, exhibits an economic effect of reducing process time through an improved deposition rate, and a nickel oxide thin film manufactured thereby has excellent physical properties, for example, excellent resistance and transparency, and thus is suitable for application to a hole transport layer of a perovskite solar cell.

Description

Method for producing bis(methylcyclopentadienyl) nickel and nickel oxide thin film using the same

The present invention relates to bis(methylcyclopentadienyl)nickel, and more particularly, to a method for producing bis(methylcyclopentadienyl)nickel.

A widely used method for manufacturing nickel oxide films used as hole transport layers (HTLs) of solar cells is to use nickel hydroxide (Ni(OH) ₂ ) as a precursor and spin coat the film onto a transparent electrode. However, there is an increasing need for films with higher transmittance to increase the efficiency of solar cells. In order to increase the transmittance, it is important to manufacture nickel oxide films with a thin thickness. Atomic layer deposition (ALD) is widely used in the manufacture of high-efficiency solar cell devices because it is easy to control the thickness and uniformity of the film.

The precursor compound for applying the above-described atomic layer deposition (ALD) method is required to have properties such as high thermal stability, high volatility, low toxicity, and high chemical stability, and also should not spontaneously decompose or side react with other substances during the process of vaporizing the compound and being transferred to the gas phase. In particular, the precursor compound for applying the atomic layer deposition (ALD) method must have a condition that it easily chemically reacts with a specific reaction gas. Therefore, there is an increasing need for a precursor material that satisfies the conditions appropriately and also satisfies properties such as high transparency of a nickel oxide thin film and uniformity of the thin film.

The technical problem of the present invention is to provide a method for producing a bis(methylcyclopentadienyl) nickel compound.

Another technical object of the present invention is to provide a nickel oxide thin film using a bis(methylcyclopentadienyl) nickel compound as a precursor and a method for producing the same.

Another technical task of the present invention is to provide a solar cell using a nickel oxide thin film manufactured by the manufacturing method of the present invention as a hole transport layer.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

The present invention may include a method for producing bis(methylcyclopentadienyl)nickel, including the steps of: introducing a methylcyclopentadiene dimer compound, an alkali metal hydroxide, and an organic solvent into a reactor; heating the reactor to a first reaction temperature and reacting to produce alkali metal methylcyclopentadienide as an intermediate product; and adding a nickel source to the reactor containing the intermediate product and the organic solvent and reacting at a second reaction temperature to produce bis(methylcyclopentadienyl)nickel as a product; wherein the first reaction temperature is higher than the second reaction temperature.

After the step of manufacturing the above product, the step of purifying the product by reduced pressure fractional distillation may be additionally included.

The above first reaction temperature may be greater than 120°C and less than 300°C.

The second reaction temperature may be 35°C to 120°C.

The above nickel source may comprise a nickel amine complex having multiple ammonia ligands.

The above nickel amine complex can be represented by the following chemical formula 2.

[Chemical formula 2]

[Ni(NH ₃ ) _n ]A ₂

In the chemical formula 2, n is an integer from 2 to 6, and A may be any one selected from F ^- , Cl ^- , Br ^- , I ^- , BF ₄ ^- , PF ₆ ^- , NO ₃ ^- and NO ₂ ^- .

The above nickel source may be any one selected from diamminenickel chloride ([Ni(NH ₃ ) ₂ ]Cl ₂ , Diamminenickel chloride), tetraamminenickel chloride ([Ni(NH ₃ ) ₄ ]Cl ₂ , Tetraamminenickel chloride), and hexaamminenickel chloride ([Ni(NH ₃ ) ₆ ]Cl ₂ , Hexaamminenickel chloride).

The above organic solvent may be a compound having a boiling point of 120 to 300°C and existing in a liquid state at room temperature.

The above organic solvent is a compound represented by the chemical formula R ₁ O (R ₂ O) _n R ₃ , wherein n is 0 to 5, R ₁ may be an alkyl group having C1 to C6, R ₂ may be an alkyl group having C1 to C3, and R ₃ may be an alkyl group having C1 to C6.

Specifically, the organic solvent may be at least one selected from diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ethertetraethylene glycol dimethyl ether, and combinations thereof.

The above manufacturing method may be performed in one reactor.

The present invention comprises a step of mounting a washed and surface-treated substrate in a chamber, and heating the substrate; a source injection step of injecting a transport gas and a nickel precursor into a reaction space on the substrate mounted inside the chamber; a first purge step of injecting a transport gas after the source injection step; a reaction step of injecting a reaction gas after the purge step; and a second purge step of injecting a transport gas after the reaction step; and the source injection step to the second purge step are repeatedly performed several to several tens of times, wherein the nickel precursor is formed by at least one of the manufacturing methods selected from claims 1 to 11.

The above nickel precursor may be bis(methylcyclopentadienyl)nickel.

The above manufacturing method may use plasma enhanced atomic layer deposition (PEALD) or thermal atomic layer deposition (Thermal ALD).

In the above manufacturing method, the deposition thickness per deposition cycle (GPC; Growth Per Cycle) may be 0.1 to 0.2 Å/cycle.

The above substrate may be a substrate including silicon on insulator (SOI), silicon carbide (SiC), indium tin oxide (ITO), indium zinc oxide (IZO), or perovskite material.

The present invention may include a nickel oxide thin film formed by the method for manufacturing a nickel oxide thin film described above.

The resistance of the above nickel oxide thin film can be 5 to 9 E-3 Ω·cm.

The thickness deviation of the above nickel oxide thin film can be -3.0 Å to +3.0 Å.

The above nickel oxide thin film can be applied as a hole transport layer of a tandem solar cell.

The present invention may include a solar cell including: a substrate; a first electrode layer formed on the substrate; an electron transport layer formed on the first electrode layer; a photoactive layer formed on the electron transport layer and including a perovskite material; a hole transport layer formed on the photoactive layer; and a second electrode layer formed on the hole transport layer; wherein the hole transport layer includes the nickel oxide thin film described above.

The above solar cell may be of tandem type.

The method for producing bis(methylcyclopentadienyl)bonkel according to one embodiment of the present invention does not require the preparation of an anhydrous solvent, and has excellent process stability by using an inexpensive and safe alkali metal hydroxide. Furthermore, bis(methylcyclopentadienyl)nickel produced thereby has excellent yield and purity. In addition, the method for producing a nickel oxide thin film according to one embodiment of the present invention has an economical effect of shortening the process time by an improved deposition rate, and the nickel oxide thin film produced thereby has excellent physical properties, such as resistance and transparency, and is therefore suitable for application as a hole transport layer of a perovskite solar cell.

FIG. 1 is a flow chart (PFD; Process flow diagram) illustrating a process for manufacturing bis(methylcyclopentadienyl) nickel according to one embodiment of the present invention.

FIG. 2 is a graph showing steps for manufacturing a nickel oxide thin film using an atomic layer deposition (ALD) method according to one embodiment of the present invention.

FIG. 3 is an ellipsometry result of a nickel oxide thin film manufactured using a nickel precursor Ni(MeCp) ₂ according to one embodiment of the present invention.

FIG. 4 is a graph showing the thickness-dependent transmittance of a nickel oxide thin film manufactured using a nickel precursor Ni(MeCp) ₂ according to one embodiment of the present invention.

The present invention can be modified in various ways and can take various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used for similar components.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries, such as those defined in common dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and shall not be interpreted in an idealized or overly formal sense, unless expressly defined in this application.

Throughout this specification, whenever a part is said to "include" a component, this does not exclude other components, but rather includes other components, unless otherwise specifically stated.

The terms “about,” “substantially,” etc., used throughout this specification are used in the sense that they are at or near the numerical value when a material tolerance is presented in the sense stated, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which exact or absolute values are stated to aid understanding of this specification.

Method for producing bis(methylcyclopentadienyl) nickel

The present invention may include a method for producing bis(methylcyclopentadienyl)nickel(II).

FIG. 1 is a flow chart (PFD; Process flow diagram) illustrating a process for manufacturing bis(methylcyclopentadienyl) nickel according to one embodiment of the present invention.

Referring to Figure 1, a methylcyclopentadiene dimer compound as a precursor, an alkali hydroxide as a reactant, and an organic solvent can be introduced into a reactor.

The above methylcyclopentadiene dimer (MCPD or MeCp dimer; Methylcyclopentadiene dimer) compound is an unsaturated hydrocarbon compound having a double ring, and specifically, may include at least one methyl group in each of two cyclopentadiene rings. The methylcyclopentadiene dimer is used as a precursor in the present invention and may be represented by the following chemical formula 1.

[Chemical Formula 1]

The above alkali hydroxide can be represented by the chemical formula MOH, wherein M is an alkali metal, and specifically, can be LiOH, NaOH or KOH. The above alkali hydroxide is used as a reactant in the method for producing bis(methylcyclopentadienyl)nickel of the present invention, and can generate water (H ₂ O) as a reaction by-product described below. Accordingly, there is an advantage of superior process stability compared to cases where conventional alkali metals that generate hydrogen gas as a by-product are used.

The above organic solvent may be an ether compound having a boiling point of 120 to 300°C and existing in a liquid state at room temperature, specifically, a linear ether compound, and more specifically, a glycol ether, which is not chemically decomposed and has thermal stability even in the first reaction temperature range described below. Meanwhile, generally and widely used general-purpose organic solvents, such as benzene, tetrahydrofuran (THF), pyridine, xylene, dimethyl sulfoxide (DMSO), etc., have relatively low boiling points, that is, they boil at the first reaction temperature and do not exist in a liquid state during the process, or they may be thermally decomposed, and thus may not be suitable for producing the bis(methylcyclopentadienyl) nickel of the present invention. Specifically, the organic solvent may be a compound having a boiling point of 120 to 300°C and existing as a liquid at room temperature, and represented by the chemical formula R ₁ O (R ₂ O) _n R ₃ , wherein n is 0 to 5, R ₁ may be a C1 to C6 alkyl group, R ₂ may be a C1 to C3 alkyl group, and R ₃ may be a C1 to C6 alkyl group. More specifically, the organic solvent may be at least one selected from diethylene glycol dimethyl ether (Diglyme), diethylene glycol diethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, and combinations thereof, and in one specific example, diethylene glycol dimethyl ether (Diglyme) may be used, but is not limited thereto.

Since the present invention uses a safe alkali metal hydroxide (MOH) that produces water (H ₂ O) as a reaction by-product, which will be described later, the risk of explosion due to the alkali metal reacting with moisture can be prevented, as is the case with conventional reactants that use alkali metals, alkali hydrides, etc. In addition, unlike conventional processes that require a moisture removal process for solvents, there is no need to prepare a separate anhydrous solvent, so the preparation process can be shortened and manufacturing costs, time, and effort can be reduced.

Thereafter, a step of heating to a first reaction temperature and reacting in a reactor containing the methylcyclopentadiene dimer compound (MeCp dimer), alkali hydroxide (MOH), and an organic solvent to produce an intermediate product can be performed.

The step of manufacturing the above intermediate product can be represented by the following reaction scheme 1.

[Reaction Formula 1]

In the above reaction scheme 1, M is an alkali metal.

The reaction represented by the above reaction formula 1 is carried out at a first reaction temperature, and specifically, the first reaction temperature may be more than 120°C and less than 300°C, more specifically, 130 to 250°C, 140 to 200°C, or, for example, 150 to 190°C.

The reaction represented by the above reaction scheme 1 may refer to a reaction in which methylcyclopentadiene (MeCp) is produced from the methylcyclopentadiene dimer (MeCp dimer) by a retro Diels-Alder reaction, followed by a reaction in which the methylcyclopentadiene (MeCp) is continuously combined with the alkali metal ion of the alkali metal hydroxide (MOH) described above. The reaction represented by the above reaction scheme 1 may be performed as a continuous reaction (one-pot reaction) in a single reactor.

In general, the retro Diels-Alder reaction is a reversible reaction and the equilibrium is biased toward the reverse reaction, so it is difficult to suppress the Diels-Alder reaction in which methylcyclopentadiene dimer (MeCp dimer) is produced from the produced methylcyclopentadiene (MeCp), and thus methylcyclopentadiene dimer (MeCp dimer) may exist with a high probability. However, in the present invention, by effectively removing water, a by-product of the above reaction scheme 1, through a high temperature reaction of 100° C. or higher, the reverse reaction is blocked, and methylcyclopentadiene (MeCp) can be obtained in a high yield.

The above alkali metal methylcyclopentadienide (MMeCp) is an intermediate product, and specifically may be lithium methylcyclopentadienide (LiMeCp), sodium methylcyclopentadienide (NaMeCp), or potassium methylcyclopentadienide (KMeCp). In one specific example, the alkali metal methylcyclopentadienide (MMeCp) may be, but is not limited to, potassium methylcyclopentadienide (KMeCp).

The reaction represented by the above reaction scheme 1 may be a liquid phase reaction.

Next, a step of adding a nickel source to the reactor containing the intermediate product and the organic solvent and reacting at a second reaction temperature to produce bis(methylcyclopentadienyl) nickel as a product can be performed. This step can be represented by the following reaction scheme 2.

[Reaction Formula 2]

In the above reaction formula 2, M is an alkali metal, and n and A are as shown in the chemical formula 2 described below.

The reaction of the above reaction scheme 2 is an irreversible reaction, and since the intermediate product, alkali metal methylcyclopentadienide (MMeCp), has low solubility in the organic solvent, it is preferable to proceed at a temperature higher than room temperature, for example, 35°C or higher, in order to increase its solubility. In addition, it is preferable to proceed at a temperature at which the product, bis(methylcyclopentadienyl)nickel, does not decompose, for example, 120°C or lower. Accordingly, the reaction of the above reaction scheme 2 is performed at the second reaction temperature, and specifically, it may be performed under conditions of 35 to 120°C, more specifically, 40 to 80°C, for example, 45 to 60°C.

The above nickel source is an ionic compound having a form in which multiple ammonia ligands are coordinately attached to a nickel (II) cation, and may specifically include a nickel amine complex. The nickel amine complex may be represented by the following chemical formula 2.

[Chemical formula 2]

[Ni(NH ₃ ) _n ]A ₂

In the above chemical formula 2, n is an integer from 2 to 6, and A is F ^- , Any one selected from Cl ^- , Br ^- , I ^- , BF ₄ ^- , PF ₆ ^- , NO ₃ ^- and NO ₂ ^- . Specifically, in the chemical formula 2, n is an even number of 2 to 6, and A is any one selected from F ^- , Cl ^- , Br ^- and I ^- .

More specifically, the nickel source may be any one selected from diamminenickel chloride ([Ni(NH ₃ ) ₂ ]Cl ₂ ), tetraamminenickel chloride ([Ni(NH ₃ ) ₄ ]Cl ₂ ), and hexaamminenickel chloride ([Ni(NH ₃ ) ₆ ]Cl ₂ ). In one specific example, the nickel source may be, but is not limited to, hexaamminenickel chloride ([Ni(NH ₃ ) ₆ ]Cl ₂ ).

The nickel source containing an ammonia ligand for supplying nickel (II) cations may be more effective in supplying anhydrous nickel. If a compound not containing an ammonia ligand, such as nickel chloride (NiCl ₂ ), is used as the nickel source, an additional moisture removal process may be required, which may reduce process efficiency. In addition, if the nickel source containing an ammonia ligand is used, the thermal stability of the precursor compound may be improved and thermal decomposition may be prevented during the deposition process described below.

The reaction of the above reaction scheme 2 can be performed until the generation of ammonia (NH ₃ ) gas stops, and after the generation of ammonia gas stops, a mixture containing the product bis(methylcyclopentadienyl) nickel, i.e., crude bis(methylcyclopentadienyl) nickel, can be obtained.

The reaction represented by the above reaction formula 2 may be a liquid phase reaction.

The product formed from the above reaction formula 2 may be a compound specifically represented by the following chemical formula 3.

[Chemical Formula 3]

Specifically, the compound of the above chemical formula 3 may be the above bis(methylcyclopentadienyl) nickel.

The above bis(methylcyclopentadienyl) nickel can exist in a liquid state at room temperature after the manufacturing reaction is completed. When bis(methylcyclopentadienyl) nickel existing in a liquid state is utilized as a nickel precursor in the manufacturing of a nickel oxide thin film described below, compared to the case of using other solid precursors, it enables more complete vaporization during the process of vaporizing the precursor solution in an evaporator, minimizes thermal decomposition, and improves deposition efficiency such as deposition thickness per cycle (GPC).

Next, a step of cooling the above product, filtering and concentrating it, and subjecting it to reduced pressure fractional distillation to produce purified bis(methylcyclopentadienyl)nickel can be performed.

In the above cooling step, the cooling temperature may be -10 to 50°C, specifically -5 to 30°C, and more specifically 0 to 10°C.

The alkali metal salt (represented as MA in the above reaction formula 2) included in the product in the above cooling step is in a solid phase and can be removed during the filtration process.

The organic solvent included in the product in the cooling step may exist in a liquid state. When the organic solvent, for example, diethylene glycol dimethyl ether (Diglyme), is used, the organic solvent can maintain a liquid state even in the cooling step, so that it can be obtained and reused in the product purification step, i.e., the fractional distillation step, or can be easily evaporated and removed. On the other hand, organic solvents used in conventional manufacturing methods, for example, dimethyl sulfoxide (DMSO) having a melting point of 19°C, exist in a solid state at the temperature of the cooling step, so that it may be difficult to apply the fractional distillation method.

The above purified bis(methylcyclopentadienyl)nickel can have a yield of 60% or more, specifically 70% or more, and a purity of 96% or more, specifically 98% or more. This means that high-quality bis(methylcyclopentadienyl)nickel can be obtained in a high yield, compared to a conventional manufacturing method using an alkali metal or alkali hydride as a reactant and using tetrahydrofuran (THF) as an organic solvent, which has a yield of not exceeding 50% and a purity of 95% or less.

Therefore, the method for producing bis(methylcyclopentadienyl)nickel according to one embodiment of the present invention has an economical effect of excellent process stability and shortening the process time by using an inexpensive and safe alkali metal hydroxide without requiring preparation of an anhydrous solvent, and further, bis(methylcyclopentadienyl)nickel produced thereby can have excellent yield and purity.

Bis(methylcyclopentadienyl)nickel manufactured through the manufacturing method of the present invention can be used in the manufacture of a nickel oxide thin film described below.

Method for manufacturing nickel oxide thin film

The method for manufacturing a nickel oxide thin film of the present invention may include: first, a step of mounting a washed and surface-treated substrate in a chamber and heating the substrate; a source injection step of injecting bis(methylcyclopentadienyl) nickel as a transport gas and a nickel precursor into a reaction space on the substrate mounted inside the chamber; a first purge step of injecting a transport gas after the source injection step; a reaction step of injecting a reaction gas after the purge step; and a second purge step of injecting a transport gas after the reaction step.

The above source injection step or the second purge step may be repeatedly performed several to several tens of times.

Specifically, bis(methylcyclopentadienyl) nickel as the nickel precursor may be formed by the above-described manufacturing method.

The above substrate is a substrate having an unrestricted form such as a flat plate or a roll, and specifically, silicon, gold (Au), silver (Ag), copper (Cu), tin (Sn), aluminum (Al), nickel (Ni), tungsten (W), chromium (Cr), zinc (Zn), platinum (Pt), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), zirconium (Zr), manganese (Mn), iridium (Ir), rhenium (Re), and ruthenium (Ru), ruthenium oxide (RuO ₂ ), titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), hafnium nitride (HfN), zirconium nitride (ZrN), tantalum silicon nitride (TaSiN), titanium silicon nitride (TiSiN), cobalt silicide (CoSi ₂ ), nickel silicide (NiSi), titanium silicide (TiSi _{2 )} . ), silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), aluminum oxide (Al ₂ O ₃ ), niobium oxide (Nb _{2 O 5 ), tantalum oxide (Ta 2 O 5 ) ,} silicon on insulator (SOI), glass, sapphire, silicon carbide (SiC), aluminum nitride (AlN), indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), perovskite materials, and combinations thereof.

More specifically, the substrate may be a substrate including silicon on insulator (SOI), silicon carbide (SiC), indium tin oxide (ITO), indium zinc oxide (IZO), or a perovskite material.

In one specific example, the substrate may be, but is not limited to, a substrate including a perovskite material used as a photoactive layer in a solar cell described below.

In the step of heating the substrate, the temperature of the substrate may be heated to 50 to 450°C, specifically 100 to 350°C, more specifically 150 to 250°C, and in one specific example 190 to 210°C.

The above transport gas is an inert gas, and specifically, any one selected from nitrogen (N ₂ ), argon (Ar), helium (He), and mixtures thereof may be used, and in one specific example, argon (Ar) may be used.

The above reaction gas is a gas containing oxygen, and any one selected from water (H ₂ O), oxygen (O ₂ ), ozone (O ₃ ), and mixtures thereof may be used, and in one specific example, oxygen (O ₂ ) may be used.

In the step of depositing the above thin film, the deposition time can be performed for, but not limited to, 0.1 seconds to 1 minute.

A method for manufacturing a nickel oxide thin film according to one embodiment of the present invention may use an atomic layer deposition method, specifically, plasma enhanced atomic layer deposition (PEALD) or thermal atomic layer deposition (Thermal ALD).

A method for manufacturing a nickel oxide thin film according to one embodiment of the present invention uses bis(methylcyclopentadienyl)nickel as a precursor containing at least one methyl group in a cyclopentadienyl ring, and can exhibit a more improved deposition rate compared to a process using a bis(cyclopentanienyl)nickel compound as a precursor containing an alkyl group having C2 to C3 carbon atoms, such as an ethyl group, an isopropyl group, or the like, instead of the methyl group, or not containing an alkyl group.

Specifically, since bis(methylcyclopentadienyl) nickel (Ni(MeCp) ₂ ) as a precursor contains a smaller number of carbon atoms than bis(ethylcyclopentadienyl) nickel (Ni(EtCp) ₂ ), and specifically, since the length of an alkyl group included in a cyclopentadienyl ring is shorter, the mobility of the precursor may be fast in the process of injecting the vaporized precursor during the deposition process, the time it takes for the precursor to reach the substrate may be shortened, and the deposition thickness per cycle may be increased. For example, in a process using bis(methylcyclopentadienyl) nickel (Ni(MeCp) ₂ ) as a precursor, the deposition thickness per cycle (GPC; Growth Per Cycle), i.e., the deposition rate may be 0.1 to 0.2 Å/cycle, specifically, 0.13 to 0.18 Å/cycle, and in one specific example, 0.15 to 0.17 Å/cycle. In contrast, in the process using bis(ethylcyclopentadienyl) nickel (Ni(EtCp) ₂ ) as a precursor, the deposition thickness per cycle (GPC) can be 0.05 to 0.1 Å/cycle, and specifically 0.07 to 0.099 Å/cycle. Therefore, faster deposition is possible in the process using bis(methylcyclopentadienyl) nickel (Ni(MeCp) ₂ ) as a precursor.

In addition, when a cyclopentanienyl nickel compound containing an alkyl group having C2 to C3 carbon atoms, such as an ethyl group or an isopropyl group, or having no alkyl group is used as a precursor, there is concern that the film quality may deteriorate because the high molecular weight and the presence of side branches may cause thermal decomposition during the deposition process, causing organic impurities or organic residues to be introduced into the film or formed on the film.

Meanwhile, bis(methylcyclopentadienyl) nickel (Ni(MeCp) ₂ ) as a precursor has a higher degree of ligand separation during the deposition process when the vaporized precursor is injected, reaches the substrate surface, and is deposited compared to bis(cyclopentadienyl) nickel (NiCp ₂ ), specifically, methylcyclopentadienyl (MeCp) ligands are better separated from the precursor compound than cyclopentadienyl (Cp) ligands. Therefore, the deposition rate can be increased when bis(methylcyclopentadienyl) nickel (Ni(MeCp) ₂ ) is used as a precursor.

In addition, when bis(cyclopentadienyl)nickel that does not contain an alkyl group in the cyclopentadienyl ring is used as a precursor, since the bis(cyclopentadienyl)nickel compound exists as a solid at room temperature, there is a lot of energy waste added in the vaporization step for application as a precursor of the atomic layer deposition method. However, when bis(methylcyclopentadienyl)nickel according to the present invention is used as a precursor, there is an economic advantage in the deposition process because a liquid precursor is used and the thin film deposition speed is fast.

Furthermore, when bis(methylcyclopentadienyl) nickel is used as a precursor, the formed thin film has good uniformity and excellent properties, such as resistance and transparency, so that high efficiency can be expected when applied as a hole transport layer of a solar cell described later.

The method for manufacturing a nickel oxide thin film according to one embodiment of the present invention can form nickel oxide having excellent thickness uniformity even when applied to a large deposition area, specifically 1 to 350 mm ² , more specifically 10 to 250 mm ² . In addition, since residue after deposition can be minimized, a high-quality nickel oxide thin film can be manufactured.

The thickness of the nickel oxide thin film according to one embodiment of the present invention may be, for non-limiting examples, 30 to 200 Å, and the above deposition may be repeated to implement a nickel oxide thin film of a desired thickness depending on the characteristics of the desired thin film.

According to one embodiment of the present invention, the deposition thickness deviation measured at a deposition area of 210 mm ² (M12 size) of the nickel oxide thin film may be -3.0 Å to +3.0 Å, specifically, -2.0 Å to +2.0 Å. Meanwhile, in the case of using Ni(EtCp) ₂ as a precursor according to a comparative example, the deposition thickness deviation may be -9.0 Å to +9.0 Å, in one example, -8.0 Å to +8.0 Å, which may exhibit a rather large deviation. Therefore, a nickel oxide thin film formed using Ni(MeCp) ₂ than a nickel precursor using Ni(EtCp) ₂ may have a lower thickness deviation and excellent uniformity.

The resistance of the above nickel oxide thin film may be, but is not limited to, 5 to 9 E-3 Ω·cm, for example, 6 to 8 E-3 Ω·cm.

A nickel oxide thin film according to one embodiment of the present invention can be preferably applied as a hole transport layer (HTL) of a tandem solar cell, but is not limited thereto.

Solar cell using nickel oxide thin film as hole transport layer

FIG. 5 is a schematic diagram showing the structure of a solar cell using a nickel oxide thin film as a hole transport layer according to one embodiment of the present invention.

Referring to FIG. 5, the solar cell (100) of the present invention may include a substrate (10), a first electrode layer (20) formed on the substrate (10), an electron transport layer (30) formed on the first electrode layer (20), a photoactive layer (40) formed on the electron transport layer (30) and including a perovskite material, a hole transport layer (50) formed on the photoactive layer (40), and a second electrode layer (60) formed on the hole transport layer (50).

The above hole transport layer may include a nickel oxide thin film formed through the above-described method for manufacturing a nickel oxide thin film.

The above substrate (10) may be any one selected from silicon oxide, aluminum oxide, glass, quartz, polyimide (PI), polyethylenenaphthalate (PEN), polyethylene terephthalate (PET), polymethylmethacrylate (PMMA), polydimethylsiloxane (PDMS), and combinations thereof.

The first electrode layer (20) and the second electrode layer (60) are an anode and a cathode, and one or both of them may be a transparent electrode layer that is transparent or translucent to allow light to enter. Specifically, the first electrode layer (20) and the second electrode layer (60), regardless of each other, may be any one selected from 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), and combinations thereof.

The electron transport layer (30) may include a metal oxide semiconductor as an electron transport material, and specifically, may include at least one selected from TiO ₂ , SnO ₂ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , W ₂ O ₅ , In ₂ O ₃ , Ga ₂ O ₃ , Nd ₂ O ₃ , PbO, CdO, and combinations thereof. In one specific example, the electron transport layer (30) may be ZnO, but is not limited thereto.

The above photoactive layer (40) includes a perovskite material, and the perovskite material is an organic metal halide perovskite, for example, CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ), CH ₃ NH ₃ PbI _3-x Cl _x (MAPbI _3-x Cl _x ), CH ₃ NH ₃ PbCl ₃ (MAPbCl ₃ ), CH ₃ NH ₃ PbI _3-x Br _x (MAPbI _3-x Br _x ), CH ₃ NH ₃ PbBr ₃ (MAPbBr ₃ ) (wherein x is 0 to 3), and any one selected from combinations thereof. In one specific example, the perovskite photoactive layer (40) may be CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ), but is not limited thereto.

The above hole transport layer (HTL; Hole transport layer) (50) may include a metal oxide semiconductor as a hole transport material, and specifically may include at least one selected from NiO, MoO ₃ , WO ₃ , V ₂ O ₅ , VO ₂ , Cu ₂ O, CuO, CrO ₂ , CoO, CuAlO ₂ , CuCrO ₂ , CuGaO ₂ , ZnRh ₂ O ₄ , GaSnO, and combinations thereof. In one specific example, the hole transport layer (50) may be NiO, but is not limited thereto.

The above hole transport layer (HTL) (50) can use a nickel oxide thin film formed by the above-described nickel oxide thin film manufacturing method.

Hereinafter, in order to explain the present invention more specifically, a preferred experimental example according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

Example 1: Preparation of bis(methylcyclopentadienyl)nickel (Ni(MeCp) ₂ )

In a nitrogen atmosphere reactor, 83.9 g (1.42 mol, 95%) of KOH, 1200 ml of Diglyme (diethylene glycol dimethyl ether), and 125.0 g (0.749 mol, 96%) of methylcyclopentadiene dimer (MeCp) are respectively supplied, and the reactor containing them is heated and stirred at a first reaction temperature (162°C) capable of cracking methylcyclopentadiene dimer to generate potassium methylcyclopentadienide (KMeCp) as an intermediate product. Next, the product including the intermediate product is cooled and transferred to an adsorption tower to adsorb water, and the solvent (Diglyme) is transferred back to the reactor and refluxed for 24 hours. Thereafter, 164.5 g (0.710 mol, 99%) of hexaamine nickel chloride (NiCl ₂ (NH ₃ ) ₆ ) is added to the reactor containing the intermediate product and Diglyme, and stirred at a synthesis temperature of 50 °C for 20 hours. Thereafter, when the generation of NH ₃ gas stops, KCl is removed by filtration, and the diglyme solvent contained in the filtrate is dried to obtain crude Ni(MeCp) ₂ . The obtained crude Ni(MeCp) ₂ is fractionally distilled under reduced pressure to obtain 115.26 g (0.5313 mol) of high-purity Ni(MeCp) ₂ . The yield at this time is 74.83%.

(1) H_NMR (400 MHz, solvent: Benzene-d6) chemical shift (multiplicity, H number) δ 206.15 (s. 6H), -253.30 (d, 8H)

(2) TGA (N ₂ 20 ml/min, 10 ℃/min heating) 50 wt% reduction temperature 156.2 ℃

(3) GC-FID (DB-1 column) purity 99.32 area%

Example 2: Preparation of bis(methylcyclopentadienyl)nickel (Ni(MeCp) ₂ )

Ni(MeCp) ₂ was obtained using the same method as in Example 1, except that the synthesis temperature was 80°C. At this time, the obtained amount of Ni(MeCp) ₂ was 81.20 g (0.3743 mol), and the yield was 52.72%.

(1) H_NMR (400 MHz, solvent: Benzene-d6) chemical shift (multiplicity, H number) δ 206.15 (s. 6H), -253.30(d, 8H)

(2) TGA (N ₂ 20 ml/min, 10 ℃/min heating) 50 wt% reduction temperature 156.2 ℃

(3) GC-FID (DB-1 column) purity 96.14 area%

Example 3: Preparation of bis(methylcyclopentadienyl)nickel (Ni(MeCp) ₂ )

Ni(MeCp) 2 was obtained using the same method as in Example 1, except that 92.01 g (0.710 mol, 99%) of nickel chloride (NiCl ₂ ) was used instead of hexaaminenickel chloride (NiCl ₂ (NH ₃ ) _{6 )} . In this case, the obtained amount of Ni(MeCp) ₂ was 79.23 g (0.3652 mol), and the yield was 51.44%.

(1) H_NMR (400 MHz, solvent: Benzene-d6) chemical shift (multiplicity, H number) δ 206.15 (s. 6H), -253.30(d, 8H)

(2) TGA (N ₂ 20 ml/min, 10 ℃/min heating) 50 wt% reduction temperature 156.2 ℃

(3) GC-FID (DB-1 column) purity 98.02 area%

Comparative Example 1: Preparation of bis(methylcyclopentadienyl)nickel (Ni(MeCp) ₂ ) using alkali hydride

In a nitrogen atmosphere, 43.90 g (1.811 mol, 99%) of NaH, 1400 ml of THF (Tetrahydrofuran), and 155 g (1.867 mol, 96%) of methylcyclopentadiene dimer (MeCp) are supplied to a reactor and reacted for 10 hours. After the reaction, solid impurities are removed through filtration. The NaMeCp solution contained in the filtrate is added to 118.50 g (0.905 mol, 99%) of NiCl ₂ dispersed in 200 ml of THF solvent at 0 ℃ for 4 hours and reacted for 10 hours. After the reaction, the temperature of the reactor is slowly raised to room temperature, NaCl is removed through filtration, and the THF solvent contained in the filtrate is dried to obtain crude Ni(MeCp) ₂ . The collected Ni(MeCp) ₂ is distilled under reduced pressure to obtain high-purity Ni(MeCp) ₂ . At this time, the yield is 34.40%.

(1) H_NMR (400 MHz, solvent: Benzene-d6) chemical shift (multiplicity, H number) δ 206.15 (s. 6H), -253.30(d, 8H)

(2) TGA (N ₂ 20 ml/min, 10 ℃/min heating) 50 wt% reduction temperature 156.2 ℃

(3) GC-FID (DB-1 column) purity 92.90 area%

Thin film manufacturing example 1: Manufacturing nickel oxide thin film using Ni(MeCp) ₂

A perovskite substrate is placed inside an atomic layer deposition (ALD) chamber and its temperature is heated to 200°C. Ni(MeCp) ₂ of Example 1 is used as a nickel precursor, and its temperature is heated to 40°C. Thereafter, argon gas is used as a transport gas and the nickel precursor is injected into the chamber for 0.2 seconds to adsorb the precursor onto the substrate (Ni source injection). Next, after purging with argon gas for 0.2 seconds (Ar purge), oxygen gas is injected for 1 second to react with the precursor and form a nickel oxide thin film. A reaction reaction proceeds (reaction gas injection). After the reaction, argon gas is purged for 0.4 seconds to remove residues decomposed by the reaction (Ar purge).

Thin film comparison example 1: Manufacturing nickel oxide thin film using Ni(EtCp) ₂

A nickel oxide thin film was manufactured using the same method as in Thin Film Manufacturing Example 1, except that Ni(EtCp) ₂ was used instead of Ni(MeCp) ₂ of Example 1 as a nickel precursor.

FIG. 2 is a graph showing steps for manufacturing a nickel oxide thin film using an atomic layer deposition (ALD) method according to one embodiment of the present invention.

Referring to Fig. 2, the Ni source injection-Ar purge-reaction gas injection-Ar purge steps of the above-described thin film manufacturing example are considered as one cycle, and the deposition process is performed by repeating the cycle several to several dozen times.

	Thin film manufacturing example 1 Precursor: Ni(MeCp) 2	Thin film comparison example 1 Precursor: Ni(EtCp) 2
Deposition thickness variation (Variation) 100Å standard, M12 size	±1.93 Å	±7.79 Å
Growth Per Cycle (GPC) (Å/cycle)	0.168	0.096
Deposition Rate (D/R) (Å/min)	7.21	3.19
Average refractive index (Avg. R.I; average refractive index)	2.28	2.298
Refractive index uniformity (R.I) (%)	0.14	0.38
Resistivity (Ω cm)	7.95 E-3	9.27 E-3

Table 1 is a table showing the deposition results of a nickel oxide thin film according to one embodiment of the present invention.

Referring to Table 1, the nickel oxide thin film manufactured through Thin Film Manufacturing Example 1 has a deposition thickness per cycle (GPC) of 0.168 Å/cycle, which is higher than 0.096 Å/cycle in Thin Film Comparative Example 1. Since the precursor Ni(MeCp) ₂ used in Thin Film Manufacturing Example 1 contains a smaller number of carbons than Ni(EtCp) ₂ in Thin Film Comparative Example 1, it can be inferred that the mobility of the vaporized precursor increases, thereby increasing the deposition thickness per cycle. In addition, it can be confirmed that the deviation of the deposition thickness of Thin Film Manufacturing Example 1 is ±1.93 Å, which is a smaller value than ±7.79 Å in Thin Film Comparative Example 1. In summary, through thin film manufacturing example 1 using Ni(MeCp) ₂ as a precursor, a nickel oxide thin film can be formed with a high deposition thickness per unit cycle, thus achieving an excellent deposition rate, and a low film thickness deviation, thereby forming a high-quality nickel oxide thin film.

FIG. 3 is an ellipsometry result of a nickel oxide thin film manufactured using a nickel precursor Ni(MeCp) ₂ according to one embodiment of the present invention.

Referring to Fig. 3, it can be confirmed through the ellipsometer results that a nickel oxide thin film manufactured using Ni(MeCp) ₂ as a nickel precursor is uniformly deposited over the entire wafer measuring 210 x 210 mm (M12 size) and has good uniformity.

FIG. 4 is a graph showing the thickness-dependent transmittance of a nickel oxide thin film manufactured using a nickel precursor Ni(MeCp) ₂ according to one embodiment of the present invention.

Referring to FIG. 4, the nickel oxide thin film of the present invention is uniformly deposited on the entire wafer having a size of 210 x 210 mm (M12 size). When the nickel oxide thin film thicknesses are 50 Å, 100 Å, 150 Å, and 200 Å, it can be seen that the transmittance of the thin film is 94.1%, 88.3%, 84.7%, and 80.5%, respectively, based on a wavelength of 600 nm.

Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples presented to help understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art to which the present invention pertains that other modified examples based on the technical idea of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (22)

1. A step of introducing a methylcyclopentadiene dimer compound, an alkali metal hydroxide and an organic solvent into a reactor;

   A step of heating the reactor to a first reaction temperature and reacting to produce alkali metal methylcyclopentadienide as an intermediate product; and

   A step of adding a nickel source to the reactor containing the intermediate product and the organic solvent, and reacting at a second reaction temperature to produce bis(methylcyclopentadienyl) nickel as a product; including,

   A method for producing bis(methylcyclopentadienyl)nickel, wherein the first reaction temperature is higher than the second reaction temperature.
2. In the first paragraph,

   A method for producing bis(methylcyclopentadienyl) nickel, further comprising, after the step of producing the above product, a step of purifying the above product by reduced pressure fractional distillation.
3. In the first paragraph,

   A method for producing bis(methylcyclopentadienyl)nickel, wherein the first reaction temperature is greater than 120°C and less than 300°C.
4. In the first paragraph,

   A method for producing bis(methylcyclopentadienyl)nickel, wherein the second reaction temperature is 35°C to 120°C.
5. In the first paragraph,

   A method for producing bis(methylcyclopentadienyl) nickel, wherein the nickel source comprises a nickel amine complex having multiple ammonia ligands.
6. In paragraph 5,

   The above nickel amine complex is represented by the following chemical formula 2, and is a method for producing bis(methylcyclopentadienyl) nickel:

   [Chemical formula 2]

   [Ni(NH ₃ ) _n ]A ₂

   In the chemical formula 2, n is an integer from 2 to 6, and A is any one selected from F ^- , Cl ^- , Br ^- , I ^- , BF ₄ ^- , PF ₆ ^- , NO ₃ ^- and NO ₂ ^- .
7. In paragraph 5,

   A method for producing bis(methylcyclopentadienyl)nickel, wherein the nickel source is any one selected from diaminenickel chloride ([Ni(NH ₃ ) ₂ ]Cl ₂ , Diamminenickel chloride), tetraamminenickel chloride ([Ni(NH ₃ ) ₄ ]Cl ₂ , Tetraamminenickel chloride), and hexaamminenickel chloride ([Ni(NH ₃ ) ₆ ]Cl ₂ , Hexaamminenickel chloride).
8. In the first paragraph,

   A method for producing bis(methylcyclopentadienyl) nickel, wherein the organic solvent is a compound having a boiling point of 120 to 300°C and existing in a liquid state at room temperature.
9. In Article 8,

   The above organic solvent is a compound represented by the chemical formula R ₁ O (R ₂ O) _n R ₃ ,

   A method for producing bis(methylcyclopentadienyl)nickel, wherein n is 0 to 5, R ₁ is an alkyl group having C1 to C6, R ₂ is an alkyl group having C1 to C3, and R ₃ is an alkyl group having C1 to C6.
10. In Article 8,

    A method for producing bis(methylcyclopentadienyl)nickel, wherein the organic solvent is at least one selected from diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ethertetraethylene glycol dimethyl ether, and combinations thereof.
11. In the first paragraph,

    A method for producing bis(methylcyclopentadienyl)nickel, wherein the above manufacturing method is performed in one reactor.
12. A step of mounting a washed and surface-treated substrate in a chamber and heating the substrate;

    A source injection step for injecting a transport gas and a nickel precursor into a reaction space on the substrate mounted inside the chamber;

    After the above source injection step, a first purge step for injecting transport gas;

    After the above purge step, a reaction step of injecting a reaction gas; and

    After the above reaction step, a second purge step for injecting transport gas is included;

    The above source injection step and the second purge step are repeatedly performed several to several tens of times,

    A method for manufacturing a nickel oxide thin film, wherein the nickel precursor is formed by at least one manufacturing method selected from claims 1 to 11.
13. In Article 12,

    A method for producing a nickel oxide thin film, wherein the nickel precursor is bis(methylcyclopentadienyl) nickel.
14. In Article 12,

    The above manufacturing method is a method for manufacturing a nickel oxide thin film using plasma atomic layer deposition (PEALD) or thermal atomic layer deposition (Thermal ALD).
15. In Article 12,

    A method for manufacturing a nickel oxide thin film, wherein the deposition thickness per deposition cycle (GPC; Growth Per Cycle) in the above manufacturing method is 0.1 to 0.2 Å/cycle.
16. In Article 12,

    A method for manufacturing a nickel oxide thin film, wherein the substrate is a substrate including a silicon on insulator (SOI), silicon carbide (SiC), indium tin oxide (ITO), indium zinc oxide (IZO), or perovskite material.
17. A nickel oxide thin film formed by at least one method selected from claims 12 to 16.
18. In Article 17,

    A nickel oxide thin film having a resistance of 5 to 9 E-3 Ω·cm.
19. In Article 17,

    A nickel oxide thin film having a thickness deviation of -3.0 Å to +3.0 Å.
20. In Article 17,

    The above nickel oxide thin film is a nickel oxide thin film applied as a hole transport layer of a tandem solar cell.
21. substrate;

    A first electrode layer formed on the above substrate;

    An electron transport layer formed on the first electrode layer;

    A photoactive layer formed on the electron transport layer and including a perovskite material;

    A hole transport layer formed on the photoactive layer; and

    A second electrode layer formed on the above hole transport layer; including,

    A solar cell, wherein the hole transport layer comprises at least one nickel oxide thin film selected from claims 17 to 20.
22. In Article 21,

    The above solar cell is a tandem type solar cell.

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