KR102216194B1 - Method of manufacturing cobalt sulfide, Solar cell including thereof and method of manufacturing the same - Google Patents

Abstract

A cobalt sulfide manufacturing method according to an embodiment comprises: a step of preparing a mixed solution of a cobalt (ll) chloride hexahydrate, a fatty acid, an amine-based compound, and a non-polar solvent; a step of producing a mixture by heat-treating the mixed solution in an inert gas: a reaction step of stirring the mixture with a solution in which powder-type sulfur has been dispersed in an amine-based compound, so as to cause a reaction at a reaction temperature between 230°C to 300°C; and a centrifugation step of centrifuging a material produced through the reaction step with a mixed solution of ethanol and toluene. A solar cell according to an embodiment comprises: a light absorption layer including a perovskite material; and an electron hole transport layer formed on the light absorption layer and including a cobalt sulfide. A solar cell manufacturing method according to an embodiment comprises the steps of: providing a first electrode; stacking an electron transporting material on the first electrode through a solution process and sintering the stacked electron transporting material to form an electron transport layer; applying a perovskite solution on an electron transport layer through a solution process and growing perovskite crystals, thereby forming a light absorption layer; stacking cobalt sulfides on the light absorbing layer through a solution process to form an electron hole transport layer; and forming a second electrode on the electron transport layer. The solar cell can be manufactured at low costs and through a simple process.

Description

TECHNICAL FIELD [Method of manufacturing cobalt sulfide, Solar cell including thereof and method of manufacturing the same}

The embodiment relates to a method of manufacturing cobalt sulfide, a solar cell including the same, and a method of manufacturing the same. Specifically, the embodiment relates to a method of manufacturing cobalt sulfide suitable for use as an inorganic hole transport material of a perovskite solar cell, a perovskite solar cell including cobalt sulfide, and a method of manufacturing the same.

Perovskite solar cells using the light absorbing layer of solar cells as organic/inorganic hybrid perovskite materials are in the spotlight as a next-generation material that can replace expensive silicon solar cells due to their high efficiency, inexpensive materials, and simple processes. .

Perovskite is suitable for solar cells due to its high absorbance to visible light and low exciton binding energy, but has a disadvantage of being very vulnerable to moisture, such as deterioration even in moisture in the air. Therefore, it is important to block the perovskite from moisture above all in order to secure the driving stability of the perovskite. Early perovskite solar cells had a problem in that perovskite crystals were separated using a polar liquid electrolyte, but in order to overcome this problem, it has become common to form a hole transport layer of an organic material.

The most common organic hole transport material in recent years is spiro-OMeTAD. According to the results of a number of studies, it seems that when spiro-OMeTAD is used as a hole transport layer, a high-efficiency solar cell exhibiting high power conversion efficiency can be manufactured. However, in order to solve the complicated synthesis process, the difficulty of the purification process, and the high manufacturing cost, additional research is required.

The biggest problem of organic hole transport materials represented by spiro-OMeTAD is that it cannot guarantee long-term stability of solar cells. The organic hole transport material is accompanied by a doping process of doping additives to overcome low electrical conductivity due to the nature of organic materials. However, additives added during the doping process are hygroscopic, which can accelerate the deterioration of the perovskite and rapidly lower the power conversion efficiency of the solar cell. Moreover, since such doping process is difficult to control, complicates the overall solar cell manufacturing process, and increases manufacturing cost, there is a room for obstacles to commercialization of perovskite solar cells.

In order to solve this problem, research to develop an inorganic hole transport material having relatively excellent electrical conductivity has been continued, but it is true that it is difficult to find a material having a band gap suitable for perovskite solar cells.

An object of the embodiment is to provide a method of manufacturing cobalt sulfide which has a band gap suitable for perovskite solar cells, has a low manufacturing cost, and is easy to stack.

Another object of the embodiment is to provide a perovskite solar cell having high long-term stability and efficiency, and a method for manufacturing the same, since it can be manufactured in a low cost and simple process by including cobalt sulfide, and does not contain hygroscopic additives.

According to an embodiment for solving the above problem, there is provided a solar cell including a light absorption layer including a perovskite material and a hole transport layer including cobalt sulfide located on the light absorption layer and the light absorption layer.

The solar cell may further include an electron transport layer located under the light absorption layer, a first electrode located under the electron transport layer, and a second electrode located on the hole transport layer.

The hole transport layer may contain an organic hole transport material, and the organic hole transport material may not contain an additive. The power conversion efficiency at a second time 1000 hours after the first time when current starts to be generated in the solar cell may be 90% or more of the power conversion efficiency at the first time.

The hole transport layer includes a plurality of layers, the cobalt sulfide is represented by CoxSy, the x and y are values within the range of 1 to 10, and the x and y of the cobalt sulfide included in each of the hole transport layers Values can be different.

The hole transport layer includes a first hole transport layer and a second hole transport layer, the first hole transport layer contains cobalt sulfide, and the second hole transport layer contains an organic hole transport material, and may not contain additives.

The cobalt sulfide is represented by CoxSy, the x and y are values within the range of 1 to 10, and the valence band of cobalt sulfide may have a value between -5.43 eV and -5.22 eV.

The cobalt sulfide is represented by CoxSy, x/y has a value of 1 or more, and a valence band of cobalt sulfide may have a value between -5.37eV and -5.25eV.

The ratio of x and y of cobalt sulfide (x:y) may be 1:1, 9:8, or 4:3.

According to an embodiment for solving the above problem, a method of manufacturing an Å positive battery includes providing a first electrode, depositing an electron transport material on the first electrode in a solution process and sintering to form an electron transport layer, and Applying a perovskite solution on the transport layer by a solution process and growing perovskite crystals to form a light absorbing layer, laminating cobalt sulfide by a solution process on the light absorbing layer to form a hole transport layer, and a hole transport layer And forming a second electrode thereon.

Forming the hole transport layer may include laminating an organic hole transport material.

According to an embodiment for solving the above problem, the method of preparing cobalt sulfide includes preparing a mixed solution of cobalt(ll) chloride hexahydrate, a fatty acid, an amine compound, and a non-polar solvent, and inactivating the mixed solution. Heat treatment in a gas phase to prepare a mixture, a solution in which sulfur in powder form is dispersed in an amine compound is stirred into the mixture to react at a reaction temperature between 230°C and 300°C, followed by a reaction step and a reaction step And centrifuging the resulting material with a mixed solution of ethanol and toluene.

The fatty acid is oleic acid, the first amine compound and the second amine compound are oleylamine, the non-polar solvent is 1-octadecene, and the heat treatment is 1 at 110°C. Time can be done.

When the reaction temperature is between 230° C. and 270° C., the mole ratio of cobalt and sulfur contained in cobalt sulfide produced by the manufacturing method becomes closer to 1:1 as the reaction temperature is lower, and 4: When the reaction temperature is close to 3, and the reaction temperature is between 270°C and 300°C, the molar ratio of cobalt and sulfur contained in the cobalt sulfide produced by the manufacturing method is closer to 4:3 as the reaction temperature decreases, and the higher the reaction temperature is 9 Can get close to :8

When the reaction temperature is 230°C, the ratio of x and y (x:y) of cobalt sulfide (CoxSy) produced by the manufacturing method is 1:1, and when the reaction temperature is 270°C, the manufacturing method The ratio (x:y) of x and y of cobalt sulfide (CoxSy) produced by is 4:3, and when the reaction temperature is 300°C, x and of cobalt sulfide (CoxSy) produced by the above production method The ratio of y (x:y) may be 9:8.

According to the embodiment, by providing a method for producing cobalt sulfide suitable for perovskite solar cells, an inorganic hole transport material having a band gap suitable for perovskite solar cells can be prepared, and a solution process is performed when forming a hole transport layer. As it can be used, the manufacturing cost of solar cells can be reduced and the manufacturing process can be simplified.

According to an embodiment, by providing a perovskite solar cell containing cobalt sulfide and a method for manufacturing the same, it is possible to manufacture a perovskite solar cell with a low cost and a simplified process, and promote perovskite deterioration due to additives By preventing the phenomenon, it is possible to secure the driving stability of the solar cell.

1 is a diagram illustrating a method of manufacturing cobalt sulfide according to an embodiment.
2(a) to 2(d) are TEM and XRD measurement results of cobalt sulfide produced according to an embodiment.
3(a) to 3(d) are XRD measurement results of cobalt sulfide produced according to the reaction temperature of the embodiment.
4 is a diagram illustrating a method of manufacturing a solar cell according to an embodiment.
5(a) and 5(b) illustrate the structure of a solar cell according to an embodiment.
6(a) to 6(d) are planar SEM and cross-section SEM measurement results of a cobalt sulfide thin film formed according to an embodiment.
7 is a diagram illustrating a valence band of cobalt sulfide generated according to an embodiment.
8 is a JV curve and power conversion efficiency graph of a solar cell according to an embodiment.
9(a) to 9(c) are photoluminescence (PL) graphs and time-resolved photoluminescence analysis graphs between the hole transport layer and the light absorption layer of the solar cell according to the embodiment.
10 is a graph showing long-term stability of a solar cell according to an embodiment.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the spirit of the invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the invention can add, change, or delete other elements within the scope of the same idea. Other embodiments included within the scope may be easily proposed, but this will also be said to be included within the scope of the inventive concept.

In addition, components having the same function within the scope of the same idea shown in the drawings of each embodiment will be described with the same reference numerals.

1. Cobalt sulfide manufacturing method

1 is a diagram illustrating a method of manufacturing cobalt sulfide according to an embodiment.

Referring to FIG. 1, the method for preparing cobalt sulfide includes preparing a mixed solution of cobalt(ll) chloride hexahydrate, fatty acid, amine compound, and non-polar solvent (S12), the mixed solution in an inert gas. Heat treatment to prepare a mixture (S14), a reaction step (S16) of stirring a solution obtained by dispersing sulfur in powder form in an amine compound into the mixture to react at a reaction temperature between 230°C and 300°C, and And centrifuging (S18) the material generated through the reaction step with a mixed solution of ethanol and toluene.

The mixed solution preparation step (S12) is a step of preparing a mixed solution of cobalt(ll) chloride hexahydrate, fatty acid, amine compound, and non-polar solvent.

The fatty acid may have a carboxyl group (-COOH). The fatty acid may have a structural formula of R-COOH. The fatty acids may include unsaturated fatty acids and saturated fatty acids. The unsaturated fatty acid may be a fatty acid having one or more double bonds or triple bonds. The unsaturated fatty acid may be selected from the group of oleic acid, linoleic acid, linolenic acid, arachidonic acid, and is not limited thereto.

The saturated fatty acid may not be a fatty acid having a double bond or a triple bond. The saturated fatty acids include propanoic acid, butyric acid, pentanic acid (Pentanoic acid or valeric acid), hexanoic acid or caproic acid, heptanoic acid or enanthic acid. Enanthic acid), Octanoic acid (Caprylic acid or Caprylic acid), Nonanoic acid (Nonanoic acid or Pelargonic acid), Decanoic acid (Decanoic acid or Capric acid), Dodecanoic acid or Ra Uric acid Lauric acid), tetradecanoic acid (Tetradecanoic acid or Myristic acid myristic acid), hexadecanoic acid (hexadecanoic acid or palmitic acid palmitic acid) and octadecanoic acid (octadecanoic acid or stearic acid stearic acid) to be selected from the group. Can be, but is not limited thereto.

The amine compound may have an amine group (-NH2). The amine compound may have a structure of R-NH2. The amine-based compound may be an aliphatic amine or an aromatic amine. The amine compound may be a monoamine or polyamine. The amine-based compound may be a primary amine, a secondary amine, or a tertiary amine. The amine-based compounds include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, nonylamine ( nonylamine), decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, Dipropylamine (dipropylamine), tributylamine (tributylamine), trioctylamine (trioctylamine) and may be selected from the group of oleylamine (oleylamine), but is not limited thereto.

The fatty acid and the amine compound may be for preventing aggregation between particles. The fatty acid and the amine compound may be for dispersing particles. The fatty acid and the amine-based compound may be used to increase the solubility of particles in a solvent. The fatty acid and the amine compound may be for capping the particles. The fatty acid and the amine compound may be for surface treatment of the particles. The fatty acid and the amine-based compound may stabilize particles. The particles may be nano-sized. The fatty acid and the amine compound may be a ligand of the particle. The fatty acid and the amine-based compound may be cobalt sulfide, cobalt sulfide nanoparticles, or a ligand of a cobalt precursor. The cobalt precursor may be a mixture containing cobalt(ll) chloride hexahydrate or cobalt.

The fatty acid and the amine-based compound may be replaced with phosphine oxide, phosphonic acid, or thiol. In addition to the fatty acid and the amine-based compound, phosphine oxide, phosphonic acid, or thiol may be added.

The non-polar solvent may be one in which the solvent molecules do not have polarity. The non-polar solvent may be one in which the solvent molecule does not have a permanent dipole. The non-polar solvent is toluene, hexane, cyclohexane, decane, dodecane, tetradecane, hexadecane, octadecane and 1 -Can be selected from the group of octadecene (1-octadecene), but is not limited thereto.

The non-polar solvent may be for dissolving the non-polar material. The non-polar solvent may be a non-polar or weakly polar solvent. The non-polar solvent may dissolve some polar substances. The non-polar solvent may be a material that does not vaporize easily at high temperatures. The non-polar solvent may be one that does not react or deform when there is a heat treatment or a reaction involving heat in a solvent.

The fatty acid may be oleic acid, the amine compound may be oleylamine, and the non-polar solvent may be 1-octadecine. The cobalt chloride hexahydrate is sold by Sigma-Aldrich Corporation (hereinafter, Aldrich) and may be a product having a purity of 98%. The oleic acid is sold by Aldrich, and may be a product having a purity of 90%. The oleylamine is sold by Tokyo Chemical Industry Co., Ltd. (hereinafter TCI), and may be a product having a purity of 50%. The 1-octadecine is sold by Aldrich, and may be a product of 90% purity.

When cobalt chloride hexahydrate (Aldrich, 98%) reacts with 0.4 mmol, 35 mmol of oleic acid (Aldrich, 90%), 35 mmol of oleylamine (TCI, 50%), 140 mmol of octadecine (Aldrich, 90%) may be included in the mixed solution.

The inert gas may be argon (Ar). The inert gas may be helium (He), neon (Ne), krypton (Kr), xenon (Xe), and radon (Rn). The inert gas may prevent an oxidation reaction or combustion of the solution in the solution.

The heat treatment temperature may be 100 ℃ to 120 ℃. The heat treatment temperature may be 110°C. The heat treatment may be performed at 110° C. for 1 hour. The heat treatment may be such that the material in the mixed solution forms a mixture. The heat treatment may be for completely dissolving cobalt chloride hexahydrate, fatty acid, and amine-based compound in the mixed solution in the non-polar solvent. The heat treatment may be for removing air or moisture contained in the mixed solution. The heat treatment may be for preparing the reaction step (S16).

The reaction step (S16) may be a reaction step in which a solution obtained by dispersing sulfur in powder form in an amine-based compound is stirred in the mixture to react at a reaction temperature between 230°C and 300°C.

The properties of the amine-based compound in the reaction step (S16) are the same as those described in the mixed solution preparation step (S12). The amine-based compound in the mixed solution preparation step (S12) and the amine-based compound in the reaction step (S16) may or may not be the same.

Sulfur in the form of powder may be sold by Aldrich. The amine compound may be oleylamine. The oleylamine is sold by Tokyo Chemical Industry Co., Ltd. (hereinafter TCI), and may be a product having a purity of 50%.

When the powder form of sulfur (Aldrich) is 2 mmol, the oleylamine (TCI, 50%) may be 5 mmol.

The reaction temperature may be a value between 230°C and 300°C. The chemical formula of cobalt sulfide produced according to the reaction temperature may be different.

The reaction temperature of cobalt sulfide produced by reaction in a non-polar solvent may be lower than the reaction temperature of cobalt sulfide produced by reaction in a polar solvent. The process of reacting cobalt sulfide in a non-polar solvent may be cheaper than a process of reacting cobalt sulfide in a polar solvent. The reaction process of cobalt sulfide produced in a non-polar solvent may be an easier and simpler process than the reaction process of cobalt sulfide produced in a polar solvent.

The centrifugation step (S18) may be a step of centrifuging the material produced through the reaction step (S16) with a mixed solution of ethanol and toluene.

The centrifugation step (S18) may be a purification step. The ratio of ethanol and toluene may be 50:1. The centrifugation speed may be 7000 rpm. The process of purifying cobalt sulfide produced in a non-polar solvent may be simpler than a process of purifying cobalt sulfide produced in a polar solvent. The process of purifying cobalt sulfide produced in a non-polar solvent may be cheaper than a process of purifying cobalt sulfide produced in a polar solvent.

Cobalt sulfide may be produced by the above manufacturing method. The properties of cobalt sulfide may vary. The cobalt sulfide may be formed into nano-sized particles. The properties of the cobalt sulfide nanoparticles may vary depending on the nanostructure, nanosize, and purity of the material. The cobalt sulfide may exist in the formula of Co ₄ S ₃ , Co ₉ S ₈ , CoS, Co ₃ S ₄ and CoS ₂ , but is not limited thereto.

2(a) to 2(d) are TEM and XRD measurement results of cobalt sulfide produced according to an embodiment. Referring to FIG. 2, cobalt sulfide produced according to the above manufacturing method may be CoS, Co ₄ S ₃ and Co ₉ S ₈ .

2(a) is a TEM measurement result of cobalt sulfide (CoS) produced according to an embodiment. 2(b) is a TEM measurement result of cobalt sulfide (Co ₉ S ₈ ) generated according to an embodiment. 2(c) is a TEM measurement result of cobalt sulfide (Co ₄ S ₃ ) generated according to an embodiment. 2(d) is an XRD measurement result of cobalt sulfide (CoS, Co ₉ S _8, and Co ₄ S ₃ ) produced according to an embodiment.

Referring to the measurement result of XRD of FIG. 2(d), it can be seen that CoS, Co ₄ S ₃ and Co ₉ S ₈ were generated by the cobalt sulfide manufacturing method. Referring to the measurement result of XRD of FIG. 2(d), it can be seen that the crystal distance for each cobalt sulfide coincides with the main peak. Referring to the TEM measurement results of FIGS. 2(a) to 2(c), it can be seen that each of the cobalt sulfide crystals was uniformly produced.

The cobalt sulfide crystal may not be formed in a heterogeneous form. The cobalt sulfide crystal may not be formed in a hollow shape. The crystal of cobalt sulfide may not be formed in a flower shape or a hollow sphere shape. The crystal of cobalt sulfide may be formed in a homogeneous form. The cobalt sulfide crystal may be formed in a hierarchical form. The crystal of cobalt sulfide may be controllable. The crystal of cobalt sulfide may be adjusted according to the reaction temperature, the fatty acid and the amine compound.

3(a) to 3(d) are XRD measurement results of cobalt sulfide produced according to the reaction temperature of the embodiment. 3(a) is an XRD measurement result of cobalt sulfide (CoS, Co ₄ S ₃ and Co ₉ S ₈ ) produced by reacting at 230°C, 270°C and 300°C. 3(b) is an XRD measurement result of a material produced at a reaction temperature of less than 230°C. 3(c) is an XRD measurement result of a material produced at a reaction temperature between 230°C and 270°C. 3(d) is an XRD measurement result of a material produced at a reaction temperature between 270°C and 300°C.

Referring to the XRD measurement results of FIGS. 3(a) to 3(d), when the reaction temperature is 230°C, CoS may be generated. When the reaction temperature is 270°C, Co ₄ S ₃ may be generated. When the reaction temperature is 300°C, Co ₉ S ₈ may be generated. The closer the reaction temperature is to 230°C, the higher the proportion of CoS may be contained in the cobalt sulfide produced. The closer the reaction temperature is to 270°C, the higher the proportion of Co ₄ S ₃ may be contained in the cobalt sulfide produced. The closer the reaction temperature is to 300° C., the higher the proportion of Co ₉ S ₈ may be contained in the cobalt sulfide produced. When the reaction temperature is between 230°C and 270°C, CoS and Co ₄ S ₃ may be generated. When the reaction temperature is between 270°C and 300°C, Co ₄ S ₃ and Co ₉ S ₈ may be generated. When the reaction temperature is between 230°C and 270°C, the mole ratio of cobalt and sulfur contained in the material produced by the preparation method becomes closer to 1:1 as the reaction temperature decreases, and the higher the reaction temperature, You can get close to 4:3. When the reaction temperature is between 270° C. and 300° C., the molar ratio of cobalt and sulfur contained in the material produced by the preparation method becomes closer to 4:3 as the reaction temperature decreases, and 9:8 as the reaction temperature increases. Can get close to The first product produced when the reaction temperature is between 230°C and 270°C contains cobalt sulfide represented by CoxSy, and the second product generated when the reaction temperature is between 270°C and 300°C is expressed as CoxSy. It may contain cobalt sulfide. In this case, an x/y average value of cobalt sulfide contained in the first product may be smaller than an x/y average value of cobalt sulfide contained in the second product.

The cobalt sulfide produced by the above manufacturing method may be in a form capable of a solution process. The solution process may be possible at low cost. The solution process may be advantageous for a large area. The cobalt sulfide may be in a form capable of forming a flat layer using a solution process. The cobalt sulfide may be in a form capable of forming a thin film using a solution process. The cobalt sulfide may have a size small enough to form a thin film using a solution process. The cobalt sulfide may be nano-sized particles. The solution process may be possible only in the case of a material having a high solubility in a solvent. The cobalt sulfide may be because it contains a ligand such as the fatty acid and an amine compound, or because it is a nano-sized particle, a solution process may be possible. The solution process is spin coating, spray coating, inkjet printing, gravure printing, nozzle printing, slit coating, bar coating. coating) and screen printing, but is not limited thereto. When the cobalt sulfide is included in a solar cell, the cobalt sulfide may be in a form capable of forming a layer in the solar cell using a solution process. The cobalt sulfide may form a thin film using a solution process. The thin film may have an excellent density.

The cobalt sulfide may be suitable for use as a catalyst for capacitors and fuel cells. The cobalt sulfide may be suitable for photoelectric devices such as CRT, LCD, EL, solar cell, and laser, and electronic devices such as memory, and various semiconductor industries and LED TVs, nonvolatile memory, laser industries, X- It may be suitable for use in all electronic devices including ray-based medical fields.

The cobalt sulfide may be a material suitable for solar cells. The cobalt sulfide may be a material suitable for perovskite solar cells. The cobalt sulfide may be a material suitable for a hole transport layer of a perovskite solar cell. The cobalt sulfide may be an inorganic hole transport material. The cobalt sulfide may be a material having a band gap or a valence band suitable for use in a hole transport layer of a perovskite solar cell.

[Experimental example]

Cobalt chloride hexahydrate (0.4mmol, Aldrich, 98%), oleic acid (35mmol, Aldrich, 90%), oleylamine (35mmol, TCI, 50%) and 1-octadecine (140mmol, Aldrich, 90%) %) preparing a mixed solution (S12), putting the mixed solution into a three-necked flask and heat-treating at 110° C. for 1 hour in an argon gas atmosphere (S14), sulfur (2 mmol, Aldrich, sulfur powder) in 5 mmol oleylamine (35 mmol, TCI, 50%) is added to the mixture with a syringe and stirred to react at a reaction temperature between 230°C and 300°C (S16), and the reaction Cobalt sulfide can be produced through a step (S18) of purifying the material produced through the step (S16) by centrifuging (7000 rpm) with a solution in which ethanol and toluene are mixed in a 50:1 ratio. have.

2. Solar cell and solar cell manufacturing method

The following relates to a solar cell 100 including cobalt sulfide and a method of manufacturing the same.

The solar cell 100 of the embodiment may generate energy from light. The solar cell 100 may separate and generate electrons and holes from light energy. The electrons and holes may recombine and disappear. The electrons and holes may move to different electrodes to generate a potential difference and a current.

4 is a diagram illustrating a method of manufacturing a solar cell according to an embodiment.

Referring to FIG. 4, the method of manufacturing the solar cell 100 includes the step of providing a first electrode 110 (S102), by laminating and sintering an electron transport material on the first electrode 110 in a solution process. Forming the electron transport layer 120 (S104), forming the light absorption layer 130 by applying a perovskite solution on the electron transport layer 120 by a solution process and growing a perovskite crystal ( S106), forming a hole transport layer 140 by laminating cobalt sulfide on the light absorption layer 130 by a solution process (S108) and forming a second electrode 150 on the hole transport layer 140 It includes (S110).

The order of the manufacturing method of the solar cell 100 may be reversed.

The solar cell 100 manufacturing method includes the steps of providing a second electrode 150, depositing cobalt sulfide on the second electrode 150 in a solution process to form a hole transport layer 140, the hole transport layer Forming a light absorbing layer 130 by applying a perovskite solution on 140 by a solution process and growing perovskite crystals, stacking an electron transport material on the light absorbing layer 130 by a solution process And sintering to form the electron transport layer 120 and forming the first electrode 110 on the electron transport layer 120.

5(a) and 5(b) illustrate the structure of a solar cell according to an embodiment.

5(a) and 5(b), the solar cell 100 may have a form in which a plurality of layers are stacked. The solar cell 100 may include a first electrode 110, an electron transport layer 120, a light absorption layer 130, a hole transport layer 140, and a second electrode 150. Each layer of the solar cell 100 may be plural. The first electrode 110, the electron transport layer 120, the light absorption layer 130, the hole transport layer 140, and the second electrode 150 may each include a plurality of layers. The solar cell 100 may further include other layers in addition to the first electrode 110, the electron transport layer 120, the light absorption layer 130, the hole transport layer 140, and the second electrode 150.

The first electrode 110 may be formed of a material having electrical conductivity. The first electrode 110 may be in the form of a film or thin film having excellent electrical conductivity. The first electrode 110 may be transparent or opaque. The first electrode 110 may include an oxide. The first electrode may include a transparent conductive oxide (TCO). The first electrode 110 includes indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), ZnO, MgO, TiOx, SnO ₂ , and doped oxides such as Ga-doped ZnO (GZO), and Al-doped AZO. ZnO) and complexes thereof may be included, but are not limited thereto. The first electrode 110 may include an organic material or a conductive polymer. The first electrode 110 is a carbon nanotube (CNT), graphene, PEDOT (Poly 3,4-ethylenedioxythiophene): PSS (Polystyrene Sulfonate), polyacetylene, polyaniline, polyti Offen (polythiophene), polypyrrole (polypyrrole), and may include a complex thereof, but is not limited thereto. The first electrode 110 may include a metal. The first electrode 110 may include a metal nanoparticle, a metal nanowire, a metal thin film, a metal mesh, and a composite thereof, but is not limited thereto. The first electrode 110 may include a composite of an oxide, an organic material, and a metal. The first electrode 110 may be a substrate on which FTO is formed.

The second electrode 150 may be formed of a material having electrical conductivity. The second electrode 150 may be in the form of a film or thin film having excellent electrical conductivity. The second electrode 150 may be transparent or opaque. The second electrode 150 may include a material selected from the group of Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, and C. The second electrode 150 may be formed of a metal oxide, a conductive polymer, a metal nanostructure, or a metal mesh, but is not limited thereto. The second electrode 150 may be formed of gold (Au). The second electrode 150 may be selected from materials and structures capable of forming the first electrode 110.

The electron transport layer 120 (ETL, electron transport layer) may transport electrons. The electron transport layer 120 may transport electrons generated separately from the light absorption layer 130. The electron transport layer 120 may move the electrons before the electrons and holes separately generated in the light absorption layer 130 are recombined and disappear. The electron transport layer 120 may prevent recombination of the electrons and holes. The electron transport layer 120 may be a layer that facilitates transport of electrons between the first electrode 110 and the light absorbing layer 130. The electron transport layer 120 may be deposited on the first electrode 110 by a solution process. The electron transport layer 120 may be laminated on the light absorption layer 130 by a solution process. The electron transport layer 120 may have a structure in which a plurality of layers are stacked.

The electron transport layer 120 may include an electron transport material. The electron transport material may change the power conversion efficiency of the solar cell 100. The electron transport material may include titanium oxide (TiOx), tin oxide (SnO2), or zinc oxide (ZnO), but is not limited thereto. The electron transport material is a fullerene (C60, C70, C80) or a fullerene derivative, PCBM ([6,6]-phenyl-C61 butyric acid methyl ester) (PCBM (C60), PCBM (C70), PCBM (C80)). It may include, but is not limited thereto. The electron transport material may include lithium floride (LiF) or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), but is not limited thereto.

The electron transport material may be a material having a conduction band suitable for the solar cell 100. The electron transport material may be a material having a conduction band suitable for the perovskite solar cell 100. The conduction band of the electron transport material may be higher than that of the material of the first electrode 110. The conduction band of the electron transport material may be lower than that of the light absorption layer 130. Electrons generated in the light absorption layer 130 may be transferred to the first electrode 110 through the electron transport layer 120.

The electron transport material may be titanium dioxide (TiO ₂ ).

The light absorption layer 130 may be a layer that separates electrons and holes by absorbing light. The light absorption layer 130 may be a layer positioned between the electron transport layer 120 and the hole transport layer 140. The light absorption layer 130 may be a layer that supplies electrons to the electron transport layer 120 and supplies holes to the hole transport layer 140. The light absorption layer 130 may be stacked on the electron transport layer 120. The light absorption layer 130 may be stacked on the hole transport layer 140. The light absorption layer 130 may include a perovskite structure material.

The perovskite material is _{CH 3 NH 3 PbBr 3 (MAPbBr} 3), CH 3 NH 3 PbI 3 (MAPbI 3), NH 2 CHNH 2 PbI 3 (FAPbI 3) and may be combinations thereof, without limitation, Does not. Since the perovskite material has a high dielectric constant, exciton binding energy is low, and thus electric charge separation may be facilitated. The perovskite material may be a material capable of thinning with a high extinction coefficient due to the direct bandgap property. The perovskite material has a long diffusion distance of charges, and may be a material capable of high efficiency when used in a solar cell due to a high open circuit voltage. The perovskite may be a material that facilitates separation and generation of electrons and holes, and relatively less likely to recombine electrons and holes.

The perovskite may have a structure vulnerable to temperature and humidity. The perovskite may have an open structure and may have a structure that is separated according to temperature and humidity. Long-term stability of the perovskite can be achieved by blocking temperature changes and moisture.

The perovskite material may be deposited through a solution process. The perovskite material may form a thin film through a solution process. The solution process may be possible at low cost. The solution process may be advantageous for a large area. The solution process may include, but is not limited to, a single-step spin coating method, a multi-step spin coating method, a dual source vapor deposition method, and a vapor-phase assist solution process method.

The valence band of the perovskite may be different depending on the material contained in the perovskite, respectively. The light absorption layer 130 may include a perovskite having a CH ₃ NH ₃ PbI ₃ structure. When the perovskite has the structural formula CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ), the valence band may have a value between -5.5 eV and -5.4 eV, specifically -5.43 eV. I can. When the perovskite has a CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ) structural formula, a conduction band may have a value between -4.0 eV and -3.8 eV, specifically -3.93 eV. have. When the perovskite has a structure of CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ), a band gap may have a value between 1.5 eV and 1.6 eV, and specifically 1.55 eV.

The hole transport layer 140 (HTL, Hole Transport Layer) may transport holes. The hole transport layer 140 may transport holes separately generated from the light absorption layer 130. The hole transport layer 140 may move the holes before the electrons and holes separated and generated in the light absorption layer 130 are recombined to disappear. The hole transport layer 140 may be a layer that facilitates transport of holes between the second electrode 150 and the light absorption layer 130. The hole transport layer 140 may be stacked on the light absorption layer 130 or the second electrode 150 by a solution process. The hole transport layer 140 may have a structure in which a plurality of layers are stacked.

The hole transport layer 140 may include a hole transport material. The hole transport material may change the power conversion efficiency of the solar cell 100. The hole transport material may be an organic hole transport material or an inorganic hole transport material. The inorganic hole transport material may be produced at a lower price than the organic hole transport material. The inorganic hole transport material may have higher electrical conductivity than the organic hole transport material. The inorganic hole transport material may have higher stability than the organic hole transport material.

The hole transport material may be a material having a highest occupied molecular orbital (HOMO) energy level suitable for the solar cell 100. The hole transport material may be a material having the highest occupied molecular orbital energy level corresponding to the valence band of the perovskite. The hole transport material may be a material having a valence band corresponding to the valence band of perovskite. The highest occupied molecular orbital energy level or valence band of the hole transport material may be higher than that of the perovskite. The molecular orbital energy level or valence band occupied by the highest level of the hole transport material may be higher than -5.43 eV. The molecular orbital energy level or valence band occupied by the highest level of the hole transport material may be lower than the conduction band of the perovskite. The molecular orbital energy level or valence band occupied by the highest level of the hole transport material may be lower than -3.93 eV. The molecular orbital energy level or valence band value occupied by the highest level of the hole transport material may change the open circuit voltage and power conversion efficiency of the solar cell 100.

The inorganic hole transport material may be cobalt sulfide. The inorganic hole transport material may be cobalt sulfide produced by the method for producing cobalt sulfide. The cobalt sulfide may be CoS, Co ₄ S ₃ , Co ₉ S ₈ or a complex thereof. The cobalt sulfide may be nano-sized particles. The cobalt sulfide may be in a form capable of forming a flat layer using a solution process. The cobalt sulfide may be laminated in the form of a thin film using a solution process. The valence band of cobalt sulfide may be higher than that of perovskite and lower than that of Spiro-OMeTAD.

The organic hole transport material is

spiro-OMeTAD(2,2',7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'spirobifluorene), 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)), P3DT(poly(3-decylthiophene)), P3DDT(poly(3-dodecylthiophene)), PPV(poly(p-phenylene vinylene)), TFB(poly(9, 9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine)), PCPDTBT(poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl-4H-cyclopenta[ 2,1-b:3,4-b']dithiophene-2,6-diyl)]), Si-PCPDTBT(poly[(4,4-bis(2-ethylhexyl)dithieno[3,2-b:2) ,3-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl]), PBDTTPD(poly((4,8-diethylhexyloxyl)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-thieny l-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(poly(triarylamine)), poly(4-butylphenyl-diphenyl-amine), PCBTDPP, PDPPDBTE, PANI, KTM3 or It may be a copolymer thereof, but is not limited thereto.

The organic hole transport material may be accompanied by a doping process including an additive to overcome low electrical conductivity. The additive may be a dopant. The additive may be hygroscopic to absorb water. The additive may absorb water and deliver it to the perovskite. The additive may include at least one of lithium bis-(trifluoromethanesulfonyl) imide (LiTFSI), 4-tert-butylpiridine (tBP), FK209, and FK269, but is not limited thereto. The organic hole transport material may be spiro-OMeTAD.

When the hole transport layer 140 includes an inorganic hole transport material and an organic hole transport material, the organic hole transport material included in the hole transport layer 140 may omit a doping process including an additive. When the hole transport layer 140 includes an inorganic hole transport material and Spiro-OMeTAD, the Spiro-OMeTAD included in the hole transport layer 140 may not undergo a doping process including an additive. When the hole transport layer 140 includes cobalt sulfide and Spiro-OMeTAD, the Spiro-OMeTAD included in the hole transport layer 140 may not undergo a doping process including an additive. The organic hole transport material may not contain an additive. The organic hole transport material can reduce the manufacturing cost by omitting the doping process and simplify the manufacturing process. In addition, the cost of materials can be lowered by replacing some of the expensive organic hole transport materials with cobal sulfide. In addition, when the inorganic hole transport material included in the hole transport layer 140 has a lower valence band than the existing hole transport material, the solar cell 100 including the hole transport layer 140 is transferred from the hole transport layer 140 to the light absorption layer 130. The charge transfer speed of can be fast, and can have higher open-circuit voltage and power conversion efficiency.

Since the organic hole transport material does not undergo the doping process, less moisture can be transferred to the perovskite than the doping process. Since the organic hole transport material does not include the additive, less moisture can be delivered to the perovskite than when the additive is included. Moisture delivered to the perovskite may separate the perovskite structure. When the structure of the perovskite is separated, the power conversion efficiency of the solar cell 100 may be lowered, and the power conversion efficiency may vary greatly over time. The power conversion efficiency and long-term stability of the solar cell 100 not including the additive may be higher than the power conversion efficiency and long-term stability of the solar cell including the additive. The doping process may include an oxidation reaction. In the doping process, it may be difficult to uniformly control the degree of oxidation. Depending on the degree of oxidation, power conversion efficiency and long-term stability of the solar cell 100 may vary. If the doping process is not constant, the power conversion efficiency of the solar electronics may not be constant. The efficiency of the solar cell 100 including the hole transport material that has not been subjected to the doping process may be higher than that of the solar cell including the hole transport material that has undergone the doping process. The solar cell 100 including the hole transport material that has not undergone the doping process can be mass-produced to have a constant efficiency than the solar cell including the hole transport material that has undergone the doping process. The solar cell 100 including the hole transport material that has not undergone the doping process may have higher long-term stability than the solar cell including the hole transport material that has undergone the doping process. The organic hole transport material may be Spiro-OMeTAD.

5(a) shows the structure of a solar cell including a single-layer hole transport layer.

The hole transport layer 140 may include an inorganic hole transport material. The inorganic hole transport material may be cobalt sulfide. The cobalt sulfide may be CoS, Co ₄ S ₃ , Co ₉ S ₈ or a complex thereof.

The hole transport layer 140 is formed of cobalt sulfide, which is an inorganic hole transport material that is cheaper than an organic hole transport material, thereby reducing a manufacturing cost. In addition, by including cobalt sulfide, which is an inorganic hole transport material, the hole transport layer 140 can omit a hygroscopic additive (dopant) or doping process, thereby reducing manufacturing cost, and long-term stability and operation of the solar cell 100 Stability can be improved. In addition, since the valence band of cobalt sulfide is lower than that of Spiro-OMeTAD, the solar cell 100 including cobalt sulfide may have a high open circuit voltage and high power conversion efficiency.

The hole transport layer 140 may be an organic/inorganic hole transport composite layer. The organic-inorganic hole transport composite layer may be defined as a composite layer of an organic hole transport material and an inorganic hole transport material. The organic-inorganic hole transport composite layer may simultaneously have the advantages of an organic hole transport material and an inorganic hole transport material. The hole transport layer 140 may not contain an additive. The organic hole transport material may be Spiro-OMeTAD, the additive may include at least one of LiTFSI and tBP, and the cobalt sulfide is at least one of CoS, Co ₄ S ₃ , Co ₉ S ₈ and a composite thereof It may include.

When the hole transport layer 140 is a composite layer of an organic/inorganic hole transport material than an organic hole transport layer, the manufacturing cost is cheaper, the manufacturing process is simplified, and open-circuit voltage, power conversion efficiency, and long-term stability may be improved. When the hole transport layer 140 is formed of a composite layer of Spiro-OMeTAD and cobalt sulfide, compared to the case where the hole transport layer 140 is formed only with Spiro-OMeTAD, the manufacturing cost is low and the manufacturing process is simplified, and the open circuit voltage, power conversion efficiency, and long-term stability are It can be improved. The above difference can be achieved by not including the additive without the low valence band of the cobalt sulfide and the hole transport layer 140 undergoing a doping process as described above.

5(b) shows the structure of a solar cell including a hole transport layer including a plurality of layers.

Referring to FIG. 5B, the hole transport layer 140 may include a plurality of layers. The hole transport layer 140 may include a first hole transport layer 141 and a second hole transport layer 142. The hole transport layer 140 may further include a plurality of hole transport layers in addition to the first hole transport layer 141 and the second hole transport layer 142. The first hole transport layer 141 may be positioned above or below the second hole transport layer 142. The position and order of the first hole transport layer 141 and the second hole transport layer 142 are not limited to the position and order indicated in the drawings.

The hole transport layer 140 may include cobalt sulfide. The hole transport layer 140 may include a plurality of hole transport layers including cobalt sulfide. Both the first hole transport layer 141 and the second hole transport layer 142 may include cobalt sulfide. Each of the first hole transport layer 141 and the second hole transport layer 142 may include at least one of CoS, Co ₄ S ₃ , Co ₉ S ₈ and a composite thereof. Chemical formulas of cobalt sulfide included in the first hole transport layer 141 and cobalt sulfide included in the second hole transport layer 142 may be different. When the hole transport layer 140 includes a plurality of layers including the cobalt sulfide, the valence bands of the cobalt sulfide included in each layer may be different, and the transport of holes may be promoted due to the difference between them. . Other effects of the hole transport layer 140 may be similar to that of a single layer.

The hole transport layer 140 may include a layer containing an inorganic hole transport material and a layer containing an organic hole transport material, respectively. The first hole transport layer 141 may include cobalt sulfide, and the second hole transport layer 142 may include an organic hole transport material. The second hole transport layer 142 may not contain an additive. The organic hole transport material may be Spiro-OMeTAD, the additive may include at least one of LiTFSI and tBP, and the cobalt sulfide is at least one of CoS, Co ₄ S ₃ , Co ₉ S ₈ and a composite thereof It may include. By forming the inorganic hole transport material represented by cobalt sulfide and the organic hole transport material in different layers, transport of holes may be promoted due to the difference in valence bands between the hole transport materials. In addition, each layer may be protected by isolating the organic hole transport material or the inorganic hole transport material from the light absorbing layer or the second electrode. In addition, the effect of the hole transport layer 140 may be similar to that of the organic-inorganic hole transport composite layer described above.

6(a) to 6(d) are planar SEM and cross-section SEM measurement results of a cobalt sulfide thin film formed according to an embodiment. 6(a) is a plane SEM measurement result of a cobalt sulfide (CoS) thin film formed according to an embodiment. 6(b) is a planar SEM measurement result of a cobalt sulfide (Co ₉ S ₈ ) thin film formed according to an embodiment. 6(c) is a planar SEM measurement result of a cobalt sulfide (Co ₄ S ₃ ) thin film formed according to an embodiment. 6(d) is a cross-sectional SEM measurement result of a solar cell formed according to the embodiment.

Referring to the planar SEM of FIGS. 6(a) to 6(c), it can be seen that a thin film including CoS, Co ₄ S ₃ or Co ₉ S ₈ was formed. The thin film may be formed using a spray and spin coating method. Referring to the cross-sectional SEM of FIG. 6(d), the solar cell 100 formed according to the embodiment can be seen. The solar cell 100 according to the embodiment has an FTO substrate as the first electrode 110, TiO ₂ as the electron transport layer 120, CH ₃ NH ₃ PbI ₃ as the light absorption layer 130, Spiro as the hole transport layer 140 -May contain gold (Au) as the organic-inorganic hole transport composite layer of OMETAD and cobalt sulfide (CoxSy) and the second electrode 150.

7 is a diagram illustrating a valence band of cobalt sulfide generated according to an embodiment. Referring to FIG. 7, the valence band of cobalt sulfide may have a value between -5.43eV and -5.22ev. The valence band of cobalt sulfide may have a value between -5.37eV and -5.25eV. The cobalt sulfide may be represented by CoxSy. The valence band of cobalt sulfide may decrease as x/y increases. The valence band of cobalt sulfide may increase as x/y decreases. When the cobalt sulfide is Co ₄ S ₃ , it may have a valence band of -5.37ev. When the cobalt sulfide is Co ₉ S ₈ , it may have a valence band of -5.31 ev. The cobalt sulfide is CoS When is, it can have a valence band of -5.25ev.

8 is a J-V curve and a power conversion efficiency graph of a solar cell according to an embodiment. Referring to FIG. 8, power conversion efficiency of the solar cell 100 including the organic/inorganic hole transport composite layer may be superior to that of the solar cell including the organic hole transport layer. The solar cell 100 including the composite layer of Spiro-OMeTAD and cobalt sulfide (CoxSy) may exhibit higher power conversion efficiency than the solar cell including the Spiro-OMeTAD and additives. The additive may include lithium (Li), specifically LiTFSI and tBP.

When the cobalt sulfide is Co ₄ S ₃ , the solar cell 100 including Spiro-OMeTAD and cobalt sulfide may have an open circuit voltage of 1.091V, and power conversion efficiency may be 18.04%. have. When the cobalt sulfide is Co ₉ S ₈ , the solar cell 100 including Spiro-OMeTAD and cobalt sulfide may have an open-circuit voltage of 1.063V, and power conversion efficiency may be 17.15%. The cobalt sulfide is CoS In this case, the solar cell 100 including Spiro-OMeTAD and cobalt sulfide may have an open circuit voltage of 1.034V, and power conversion efficiency may be 16.83%. These are all shown to be superior to the open circuit voltage (1.019V) and power conversion efficiency (16.7%) of the solar cell 100 including Spiro-OMeTAD and additives.

As the cobalt sulfide has a lower valence band, the open-circuit voltage of the solar cell 100 including the cobalt sulfide may increase. As the cobalt sulfide has a lower valence band and the open-circuit voltage of the solar cell 100 including cobalt sulfide increases, the power conversion efficiency of the solar cell 100 including cobalt sulfide may increase.

9(a) to 9(c) are photoluminescence (PL) graphs and time-resolved photoluminescence analysis graphs between the hole transport layer and the light absorption layer of the solar cell according to the embodiment. 9(a) is a photoluminescence (PL) graph between the hole transport layer 140 and the light absorption layer 130 of the solar cell 100 according to the embodiment, and FIG. 9(b) is an enlarged view. 9(c) is a graph of a time resolved photoluminescence analysis between the hole transport layer 140 and the light absorption layer 130 of the solar cell 100.

9(a) to 9(c), the charge transfer speed between the interface of the hole transport layer 140 and the light absorption layer 130 is organic-inorganic hole transport compared to the case of using the organic hole transport layer (Spiro-OMeTAD). It may be faster when a composite layer (a composite layer of Spiro-OMeTAD and cobalt sulfide) is used as the hole transport layer 140. The charge transfer rate between the interface of the hole transport layer 140 and the light absorption layer 130 was highest in the case of the composite layer of Spiro-OMeTAD and Co ₄ S ₃ , followed by the composite of Spiro-OMeTAD and Co ₉ S ₈ . Layer, Spiro-OMeTAD and CoS in order. That is, as the valence band of cobalt sulfide is lower, charge transfer between the interface of the hole transport layer 140 and the light absorption layer 130 may be faster. The power conversion efficiency of the solar cell 100 may be high when charge transfer between the interface of the light absorption layer 130 and the hole transport layer 140 is fast. As the valence band of cobalt sulfide is lower, power conversion efficiency of the solar cell 100 including the cobalt sulfide may be higher.

10 is a graph showing long-term stability of a solar cell according to an embodiment.

Referring to FIG. 10, long-term stability of a solar cell 100 including an organic/inorganic hole transport composite layer may be superior to that of a solar cell including an organic hole transport layer. That is, the long-term stability of the solar cell 100 including Spiro-OMeTAD and cobalt sulfide (CoxSy) may be superior to that of a solar cell including only Spiro-OMeTAD. The solar cell 100 including the composite layer of Spiro-OMeTAD and cobalt sulfide (CoxSy) may have high efficiency even after 1000 hours. The solar cell 100 including the composite layer of Spiro-OMeTAD and cobalt sulfide (CoxSy) may exhibit 90% or more of the initial efficiency even after 1000 hours. High long-term stability of the solar cell 100 including the composite layer of Spiro-OMeTAD and cobalt sulfide (CoxSy) can be achieved by not including the additive. By not including the additive, the hole transport layer 140 may not transfer moisture to the light absorption layer 130 of the solar cell 100. High long-term stability of the solar cell 100 including the composite layer of Spiro-OMeTAD and cobalt sulfide (CoxSy) can be achieved by omitting the doping process. By omitting the doping process, the hole transport layer 140 may not be oxidized compared to the case of undergoing the doping process, and the light absorption layer 130 of the solar cell 100 may not be oxidized.

The following is an example of manufacturing a solar cell 100 including the hole transport layer 140 composed of a composite of Spiro-OMeTAD and the cobalt sulfide. The solar cell 100 may be formed in the following manner, but is not limited thereto.

[Experimental example]

The first electrode 110 is prepared. The first electrode 110 is washed in detergent, DI water, and isopropanol for 15 minutes using a vibrator. Thereafter, the first electrode 110 is subjected to UV-ozone treatment for 20 minutes to make the surface of the first electrode 110 hydrophilic. After laminating l-TiO2 solution (Sharechem) on the washed first electrode 110 by spin coating for 4000 pm for 30 seconds, meso-TiO ₂ paste (1g, Sharechem) was laminated and sintered at 500°C for 1 hour The process proceeds to form the electron transport layer 120.

Lead iodide (PbI2, 461mg, Alfa Aesar), methylammonium halide (MAI, 159mg), and dimethylsulfoxide (DMSO, 78mg) were added to dimethylformamide (DMF, 600mg, Alfa). Aesar) solution to prepare a perovskite solution. The prepared perovskite solution is deposited on the electron transport layer 120 on which the sintering process is completed by spin coating at 4000 rpm for 30 seconds. During spin coating, diethyl ether (0.5ml) is added to prepare a highly crystalline perovskite (CH ₃ NH ₃ PbI ₃ ) light absorbing layer 130.

A hole transport layer 140 is formed by laminating cobalt sulfide (CoxSy) and spiro-OMeTAD on the light absorption layer 130 on which the perovskite crystal growth has been completed by spraying and spin coating. A second electrode 150 is formed by depositing a gold (Au) electrode having a thickness of 80 nm on the hole transport layer 140.

In the above, the configuration and features of the present invention have been described based on the embodiments according to the present invention, but the present invention is not limited thereto, and it is understood that various changes or modifications can be made within the spirit and scope of the present invention. It will be apparent to those skilled in the art, and therefore, such changes or modifications are found to belong to the appended claims.

Claims (15)

A light absorbing layer comprising a perovskite structure material; And
Including; a hole transport layer located on the light absorption layer and containing cobalt sulfide,
The cobalt sulfide is represented by CoxSy, and x and y are values within the range of 1 to 10,
The valence band of the cobalt sulfide has a value between -5.43 eV and -5.22 eV.
Solar cell.
The method of claim 1,
An electron transport layer located under the light absorption layer;
A first electrode located under the electron transport layer; And
A second electrode positioned on the hole transport layer; further comprising
Solar cell.
The method of claim 1,
The hole transport layer contains an organic hole transport material,
The organic hole transport material does not contain additives
Solar cell.
The method of claim 3,
The power conversion efficiency at a second time 1000 hours after the first time when the current starts to be generated in the solar cell is 90% or more of the power conversion efficiency at the first time.
Solar cell.
The method of claim 1,
The hole transport layer includes a plurality of layers,
The cobalt sulfide is represented by CoxSy, and x and y are values within the range of 1 to 10,
The values of x and y of the cobalt sulfide (CoxSy) included in each of the hole transport layers are different
Solar cell.
The method of claim 1,
The hole transport layer includes a first hole transport layer and a second hole transport layer,
The first hole transport layer contains cobalt sulfide,
The second hole transport layer contains an organic hole transport material, and does not contain additives.
Solar cell.
delete The method of claim 1,
The cobalt sulfide is represented by CoxSy, and x/y has a value of 1 or more,
The valence band of the cobalt sulfide has a value between -5.37eV and -5.25eV.
Solar cell.
The method of claim 8,
The ratio of x and y of cobalt sulfide (x:y) is 1:1, 9:8 or 4:3
Solar cell.
Providing a first electrode;
Depositing an electron transport material on the first electrode by a solution process and sintering to form an electron transport layer;
Forming a light absorption layer by applying a perovskite solution on the electron transport layer by a solution process and growing a perovskite crystal;
Forming a hole transport layer by laminating cobalt sulfide on the light absorbing layer by a solution process; And
Including; forming a second electrode on the hole transport layer,
The cobalt sulfide is represented by CoxSy, and x and y are values within the range of 1 to 10,
The valence band of the cobalt sulfide has a value between -5.43 eV and -5.22 eV.
Solar cell manufacturing method.
The method of claim 10,
The forming of the hole transport layer includes laminating an organic hole transport material.
Solar cell manufacturing method.
Preparing a mixed solution of a cobalt chloride hexahydrate, a fatty acid, a first amine compound, and a non-polar solvent;
Heat-treating the mixed solution in an inert gas to prepare a mixture;
A reaction step of reacting a solution obtained by dispersing sulfur in powder form in a second amine compound into the mixture and reacting at a reaction temperature between 230°C and 300°C; And
Including; centrifuging the material produced through the reaction step with a mixed solution of ethanol and toluene
Method for producing cobalt sulfide.
The method of claim 12,
The fatty acid is oleic acid, the first amine compound and the second amine compound are oleylamine, the non-polar solvent is 1-octadecene,
The heat treatment is performed at 110° C. for 1 hour
Method for producing cobalt sulfide.
The method of claim 12,
When the reaction temperature is between 230° C. and 270° C., the mole ratio of cobalt and sulfur contained in cobalt sulfide produced by the preparation method becomes closer to 1:1 as the reaction temperature is lowered, and the reaction temperature is higher. The more it gets closer to 4:3,
When the reaction temperature is between 270° C. and 300° C., the molar ratio of cobalt and sulfur contained in cobalt sulfide produced by the preparation method becomes closer to 4:3 as the reaction temperature decreases, and 9 as the reaction temperature increases. Getting closer to eight
Method for producing cobalt sulfide.
The method of claim 12,
When the reaction temperature is 230°C, the ratio (x:y) of x and y of cobalt sulfide (CoxSy) produced by the manufacturing method is 1:1,
When the reaction temperature is 270°C, the ratio of x and y (x:y) of cobalt sulfide (CoxSy) produced by the manufacturing method is 4:3,
When the reaction temperature is 300°C, the ratio of x and y (x:y) of cobalt sulfide (CoxSy) produced by the above manufacturing method is 9:8
Method for producing cobalt sulfide.

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