KR101462020B1 - Fabrication Method of Efficient Inorganic／Organic Hybrid Solar Cells Based on Metal Chalcogenide as a Light Harvesters - Google Patents

Abstract

The present invention relates to a method of fabricating inorganic/organic hybrid solar cells. More particularly, the present invention relates to a method of fabricating a high efficient solar cell which greatly improves efficiency by using a defect-cured light harvester with a method of coating the surface of a chalcogenide light harvester formed in a porous light electrode by a solution method with a chalcogenide-containing organic material and performing a thermal process.

Description

Technical Field [0001] The present invention relates to a method of manufacturing a high-efficiency organic / inorganic hybrid solar cell based on a chalcogen compound light absorber,

The present invention has high efficiency and excellent stability, and can be applied to a very simple manufacturing process using a solution. Therefore, it is possible to provide a non-organic solar cell which can have an extremely low production cost as compared with a known silicon or compound semiconductor- More particularly, the present invention relates to a solar cell having extremely improved efficiency by significantly lowering the defect concentration of a metal chalcogen compound as a light absorber, and a manufacturing method thereof.

Research on renewable and clean alternative energy sources such as solar energy, wind power, and hydro power is actively being conducted to solve the global environmental problems caused by depletion of fossil energy and its use.

Among these, there is a great interest in solar cells that change electric energy directly from sunlight. Here, a solar cell refers to a cell that generates a current-voltage by utilizing a photovoltaic effect that absorbs light energy from sunlight to generate electrons and holes.

Currently, np diode-type silicon (Si) single crystal based solar cells with a light energy conversion efficiency of more than 20% can be manufactured and used for actual solar power generation. Compound semiconductors such as gallium arsenide (GaAs) There is also solar cell using. However, since such a metal chalcogen compound-based solar cell requires a material purified to a very high purity for high efficiency, a large amount of energy is consumed in the purification of the raw material, and in the process of making single crystal or thin film using raw material, expensive process equipment Is required to lower the manufacturing cost of the solar cell, which has been a hindrance to a large-scale utilization.

Accordingly, in order to manufacture solar cells at a low cost, it is necessary to drastically reduce the cost of materials or manufacturing processes used as the core of solar cells. As an alternative to metal chalcogen compound-based solar cells, Dye-sensitized solar cells and organic solar cells have been actively studied.

The working principle of the dye-sensitized solar cell is that when dye molecules chemically adsorbed on the porous photocathode absorb solar light, dye molecules generate electron-hole pairs and electrons are injected into the conduction band of the semiconductor oxide used as a porous photocathode And is transferred to the transparent conductive film to generate a current. The remaining holes in the dye molecules are transferred to the photocathode by hole conduction or hole-conducting polymers by the oxidation-reduction reaction of liquid or solid electrolyte, forming a complete solar cell circuit, .

Organic photovoltaic (OPV) organic solar cells are characterized by being composed of organic materials with electron donor (D or often called hole acceptor) characteristics and electron acceptor (A) characteristics. When a solar cell made of organic molecules absorbs light, electrons and holes are formed. This is called an exciton.

The exciton migrates to the D-A interface and the charge is separated, the electrons are transferred to the electron acceptor, and the holes are transferred to the electron donor to generate the photocurrent. The combination of materials mainly used in organic solar cells is organic (D) - fullerene (A), organic (D) - organic (A), and organic (D) - nano inorganic (A).

Since the distance that the exciton generated from the electron donor can travel normally is very short, about 10 nm, the efficiency is low due to the low light absorption because the photoactive organic material can not be stacked thickly. Recently, the so- called bulk heterojunction (BHJ) ) Concept and the development of a donor organic material having a small bandgap which is easy to absorb a wide range of solar light, efficiency is greatly increased and an organic solar cell having an efficiency of about 6.77% is reported.

The present applicant has disclosed a Korean patent No. 1172534, which discloses a low-cost and high-efficiency dye-sensitized solar cell (DSSC) structure in which a wide band of solar energy is easily absorbed from a visible ray to a near- It combines the advantages of an inorganic thin-film solar cell based on a co-based compound and the advantages of an organic solar cell that can be manufactured at low cost by a solution process, And a low-cost solar cell by the application of a low-cost process.

As a result of intensive research on the proposed solid-state heterojunction solar cell, the Applicant has found that the efficiency of a solar cell is remarkably reduced due to defects of an optical absorber as an inorganic semiconductor, and in order to prevent the efficiency from being deteriorated due to such defects, As a result, the present invention has been filed.

Korea Patent No. 1172534

Nano Letters, vol. 10, p. 2609-2612 (2010); Nano Letters, vol 11, 4789-4793 (2011)

The present invention provides a method of manufacturing a solar cell having a very high photoelectric conversion efficiency by manufacturing a light absorber having a high crystallinity and a low defect, and a high efficiency solar cell manufactured by such a manufacturing method.

A method of manufacturing a solar cell according to the present invention includes the steps of: a) forming a porous inorganic electron transporting layer; b) forming a metal chalcogen compound as a light absorber on the surface of the porous inorganic electron transporting layer; c) forming a chalcogen-containing organic coating layer by applying a solution in which a chalcogen-containing organic material is dissolved in a porous inorganic electron transport layer formed with a metal chalcogen compound; d) heat treating the chalcogen-containing organic coating layer; And e) forming a hole transporting layer by applying a hole-transporting organic material on the porous inorganic electron-transporting layer.

In the method of manufacturing a solar cell according to an embodiment of the present invention, the metal chalcogen compound may include iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo), cadmium (Cd) , Gallium (Ga), indium (In), tin (Sn), lead (Pb), antimony (Sb) and bismuth (Bi).

In the method of manufacturing a solar cell according to an embodiment of the present invention, the chalcogen-containing organic material may be selected from materials satisfying the following Chemical Formulas 1 to 3.

(Formula 1)

X is a chalcogen element, R ₁ and R ₂ are, independently of each other, -NR ₁₁ R ₁₂ , (C 1 -C 20) alkyl, (C 6 -C 20) aryl or (C 6 -C 20) C20) alkyl, and R < ₁₁ > and R < ₁₂ > are independently of each other hydrogen or (C1-C20) alkyl.

(2)

In Formula (2), X is a chalcogen element, and R ₃ and R ₄ are independently of each other hydrogen or (C 1 -C 20) alkyl.

(Formula 3)

이며, R₂₁은 (C1-C20) 알킬, (C6-C20) 아릴 또는 아미노이며, R₅는 수소 또는 (C1-C20)알킬이다.X is a chalcogen element, n is an integer from 1 to 5, R is independently from each other hydrogen, halogen, (C1-C20) alkyl or

And, R ₂₁ is (C1-C20) alkyl, (C6-C20) aryl or amino, R ₅ is hydrogen or (C1-C20) alkyl.

In the method of manufacturing a solar cell according to the present invention, the chalcogen-containing organic material may be selected from a material satisfying the following Formula 1-1 or Formula 1-2.

(1-1)

In formula (1-1), X is a chalcogen element, and R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ independently of one another are hydrogen or (C 1 -C 20) alkyl.

(1-2)

In Formula 1-2, X is a chalcogen element, R ₄₁ and R ₄₂ are independently of each other hydrogen or (C 1 -C 20) alkyl, and R ₄₃ is (C 1 -C 20) alkyl.

In the method for manufacturing a solar cell according to an embodiment of the present invention, the concentration of the chalcogen-containing organic material in the solution may be 10 to 200 mg / mL.

In the method of manufacturing a solar cell according to an embodiment of the present invention, the chalcogen-containing organic coating layer may be thermally decomposed by the heat treatment.

In the method of manufacturing a solar cell according to an embodiment of the present invention, the heat treatment may be performed at 150 to 350 ° C in an inert atmosphere.

In the method of manufacturing a solar cell according to an embodiment of the present invention, a step of forming a metal oxide thin film on the first electrode before step a); And forming a second electrode over the hole transport layer after step e).

In the method of manufacturing a solar cell according to an embodiment of the present invention, step b) may include chemical bath deposition (CBD); And a successive ionic layer adsorption and reaction method (SILAR).

In the method of manufacturing a solar cell according to an embodiment of the present invention, after the step b), a step of heat-treating the porous inorganic electron-transporting layer on which the light absorber is formed in an inert atmosphere at a temperature of 200 to 400 ° C .

In the method of manufacturing a solar cell according to an embodiment of the present invention, the porous inorganic electron transporting layer may include metal oxide particles, and the metal oxide particles may be dispersed in the metal precursor solution before the step b) And impregnating the porous inorganic electron transport layer and subjecting the porous inorganic electron transport layer to heat treatment.

In the method of manufacturing a solar cell according to an embodiment of the present invention, the application of step c) may be performed by spin coating.

The present invention includes a solar cell manufactured by the above-described manufacturing method.

A solar cell according to the present invention comprises a porous inorganic electron transport layer; A light absorber located on the surface of the porous inorganic electron transporting layer and comprising a metal chalcogen compound satisfying a stoichiometric ratio; And an organic hole transporting layer filling the pores of the porous inorganic electron transporting layer where the light absorber is located and covering the porous inorganic electron transporting layer.

A method of manufacturing a solar cell according to the present invention is a method of manufacturing a solar cell, which comprises forming a coating layer of a chalcogen-containing organic material on a metal chalcogen compound-based light absorber and then performing heat treatment to heal defects existing in the metal chalcogen compound, It is possible to manufacture a solar cell having an excellent efficiency by an extremely simple and easy method such as solution coating and heat treatment, since the photoelectrons and / or photo holes generated by recombination of the generated photoelectrons and / or photo holes can be prevented from disappearing.

FIG. 1 is a graph showing a current-voltage (IV) curve and a quantum yield difference of the solar cell manufactured in Example 1 and Comparative Example 1,
2 is a graph showing X-ray photoelectron spectroscopy (SEM) analysis results of Sb ₂ S ₃ prepared by the methods of Examples 1 and 2 and Comparative Example 1

Hereinafter, a method of manufacturing a solar cell according to the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

A method of manufacturing a solar cell according to the present invention includes the steps of: a) forming a porous inorganic electron transporting layer; b) forming a metal chalcogen compound as a light absorber on the surface of the porous inorganic electron transporting layer; c) forming a chalcogen-containing organic coating layer by applying a solution in which a chalcogen-containing organic material is dissolved in a porous inorganic electron transport layer formed with a metal chalcogen compound; d) heat treating the chalcogen-containing organic coating layer; And e) forming a hole transporting layer by applying a hole-transporting organic material on the porous inorganic electron-transporting layer.

More specifically, the method for fabricating a solar cell according to the present invention comprises the steps of forming a porous inorganic electron transport layer (electron transport layer formation step) on top of a first electrode or a first electrode stacked on a transparent substrate; Forming a light absorber that is an inorganic metal chalcogen compound that absorbs sunlight to generate a pair of photoelectrons and light holes so as to be in contact with the surface of the porous electron transport layer (light absorber forming step); Coating a solution of the chalcogen-containing organic material dissolved in the porous inorganic electron transport layer on which the metal chalcogen compound is formed to form a chalcogen-containing organic material coating layer (organic material coating step); Heat treating the chalcogen-containing organic coating layer (coating layer heat treatment step); Forming a hole transporting layer (a hole transporting layer forming step) by applying a hole transporting organic material on the porous inorganic electron transporting layer; And forming a second electrode on the hole transporting layer (a counter electrode forming step).

The porous electron transport layer may be a porous metal oxide layer, and the porous electron transport layer formation step may be a step of applying a slurry containing metal oxide particles, followed by heat treatment to form a porous electron transport layer.

The electron transport layer forming step uses a slurry containing metal oxide particles, and the application of the slurry is performed by screen printing; Spin coating; Bar coating; Gravure coating; Blade coating; And roll coating. ≪ / RTI >

The metal oxide particles constituting the electron transport layer may be selected from one or more of TiO ₂ , SnO ₂ , ZnO, WO ₃ and Nb ₂ O ₅ , and more preferably TiO ₂ .

The concentration of the slurry, the pressure applied at the time of application, the amount of the slurry contained in the slurry, and the amount of the slurry contained in the slurry, so that the specific surface area of the electron transport layer produced by the heat treatment after the slurry applied in the step of forming the electron transport layer is dried is 10 to 100 m ² / One or more factors selected from the average size of the metal oxide particles, the particle size distribution of the metal oxide particles contained in the slurry, the heat treatment temperature and the heat treatment time can be adjusted.

The factors that greatly affect the specific surface area and the open pore structure of the electron transport layer are the average particle size of the metal oxide particles and the heat treatment temperature performed to form the electron transport layer. Preferably, the average particle size of the metal oxide particles is 5 to 100 nm, and the heat treatment is performed in air at 200 to 550 ° C. After the heat treatment, a step of irradiating ultraviolet rays and ozone (UV / ozone) to the heat-treated electron transfer layer may be further performed to improve wettability with organic substances.

It is preferable that the coating thickness of the slurry is adjusted so that the thickness of the electron transport layer formed by the heat treatment after the slurry applied in the electron transport layer formation step is dried is 0.1 to 5 占 퐉.

In forming the electron transport layer, it is preferable that an electron transport layer post-treatment step of impregnating the porous electron transport layer with the metal precursor solution containing the metal element of the metal oxide is further performed.

Preferably, the metal precursor of the electron transport layer post-treatment step is a metal halide selected from one or more metal chlorides, metal fluorides, and metal iodides, and the metal precursor solution is a solution in which the metal precursor is dissolved at a low concentration of 10 to 40 mM . In the electron transport layer post-treatment step, it is preferable that the impregnation is performed for 6 to 18 hours, and then the substrate is separated and recovered.

When the porous electron transport layer produced by the heat treatment after applying the slurry containing the metal oxide particles in the electron transport layer post-treatment step is left in a very dilute metal precursor solution, as the time increases, Small metal oxide particles are produced by attaching to the porous electron transport layer.

The extremely fine metal oxide particles (post-treatment particles) produced by such post-treatment are present between the particles and the particles of the porous electron transport layer having a relatively large defect, and the electron flow of the electron transport layer having the porous structure Thereby increasing the efficiency of the device and increasing the specific surface area of the electron transporting layer to increase the adhesion amount of the light absorber.

After the impregnation of the metal precursor solution in the electron transport layer post-treatment step, the heat treatment may be performed, and the heat treatment performed after impregnation with the metal precursor solution is performed at 200 to 550 ° C in the air . More preferably, the heat treatment performed after the post-treatment is an extension of the heat treatment for forming the electron transport layer, and the extension of the heat treatment is to stop the heat treatment for forming the electron transport layer in the middle, The transfer layer is impregnated for a predetermined time, separated and recovered, and then the heat treatment for forming the electron transport layer is resumed.

Before the electron transport layer formation step is performed, a thin film of metal oxide may be formed on the first electrode (thin film formation step). The thin film forming step may be performed by chemical or physical vapor deposition used in a conventional semiconductor process, and may be performed by a spray pyrolysis method (SPM). At this time, the metal oxide of the metal oxide thin film is preferably the same as the metal oxide of the electron transport layer.

The light absorber-forming step is a step of applying (a method of attaching by adsorption) a dispersion of nanoparticles of colloidal phase; Spray pyrolysis method (SPM); Chemical solution deposition (CBD); And SILAR (Successive Ionic Layer Adsorption and Reaction method). However, it is preferable that the surface contact between the metal oxide particles and the metal chalcogen compound is easily formed, and the porous electron transfer In order to form inorganic nanoparticles uniformly distributed on the surface of the layer (including the surface by pores), a chemical solution deposition method (CBD) and a successive ionic layer adsorption and reaction (SILAR) It is even more desirable that the method is performed in one or more selected ways.

The metal chalcogen compound (light absorber) may be in the form of a film covering the surface of the electron transport layer including a surface of a plurality of particles or pores separated from each other. The film-shaped metal chalcogen compound (light absorber) may be in the form of a continuous layer or a discontinuous layer covering the surface of the metal oxide particles constituting the electron transport layer.

In view of easy control of the shape of the metal chalcogenide compound such as the island-shaped metal chalcogenide compound or the film-shaped metal chalcogen compound, step b) may be carried out by a chemical bath deposition method (CBD) ) And a successive ionic layer adsorption and reaction method (SILAR).

In the case of SILAR, the precursor of each element constituting the metal chalcogen compound is dissolved by the precursor to prepare a precursor solution, then the first electrode having the porous electron transfer layer is alternately immersed in the precursor solution, A metal chalcogen compound attached to the surface of the metal oxide particles or a metal chalcogen compound forming a film on the surface of the metal oxide particles can be prepared by adjusting the number of repetition of the unit process. Chlorides, iodides, fluorides, nitrides, organic materials or minerals can be used as precursors. As a non-limiting example, when the metal chalcogen compound is Sb ₂ S ₃ , Sb ₂ O ₃ can be used as a precursor of Sb by dissolving it in a complexing agent such as tartaric acid. As a precursor of S, Na ₂ S ₂ O ₃ can be used.

In the case of CBD, a precursor solution of each element constituting the metal chalcogen compound is dissolved by precursors to prepare a precursor solution. Then, each precursor solution is mixed to prepare a mixed solution, and a first electrode, To prepare a light absorber. At this time, the metal chalcogen compound adhered to the surface of the metal oxide particles in the form of islands and the metal chalcogen compound or the metal chalcogen compound forming the film on the surface of the metal oxide particles are controlled by adjusting the precursor concentration of the mixed solution or the time of impregnation into the mixed solution Can be prepared. Chlorides, iodides, fluorides, nitrides, organic materials or minerals can be used as precursors. As a non-limiting example, when the metal chalcogen compound is Sb ₂ S ₃ , a chloride of Sb is used as a precursor of Sb, and a sulfur-containing organic substance or a sulfur-containing inorganic substance may be used as a precursor of S, , And Na ₂ S ₂ O ₃ may be used as a sulfur-containing inorganic material. The CBD is preferably carried out at 10 캜 or lower.

The metal chalcogen compound prepared in the light absorbing layer forming step may be at least one selected from the group consisting of Fe, Co, Ni, Cu, Mo, Cd, Ga, Chalcogen compound of at least one selected from the group consisting of In, Sn, Pb, Antimony, Sb and Bi. Specifically, the metal chalcogen compound is at least one selected from the group consisting of Fe, Co, Ni, Cu, Mo, Cd, Ga, Selenium, tellurium, mixtures thereof, or solid solutions of at least one selected metal selected from the group consisting of tin (Sn), lead (Pb), antimony (Sb) and bismuth (Bi) More specifically, the metal knife kojen compounds are CdS, CdSe, CdTe, PbS, PbSe, Bi 2 S 3, Bi 2 Se 3, InP, Sb 2 S 3, Sb 2 Se 3, SnS x (1≤x≤2 ), NiS, CoS, FeS _y (1? _Y ? ₂ ), In ₂ S ₃ , MoS, MoSe and their alloys.

When the metal chalcogen compound is prepared as an island-like particle, the mean diameter of the particles is preferably 0.5 nm to 10 nm, and when the metal chalcogen compound is prepared in the form of a discontinuous layer or a continuous layer, And is preferably a film having a thickness of 0.5 nm to 20 nm and composed of grains having a thickness of from 10 nm to 10 nm.

After the light absorber forming step is performed, a heat treatment may be further performed to increase the crystallinity of the metal chalcogen compound formed on the surface of the porous electron transport layer (including the surface by pores) before the formation of the organic coating layer. Such a heat treatment can be performed in an inert atmosphere at a temperature of 200 to 400 DEG C for 1 minute to 30 minutes in view of suppressing the oxidation of the metal chalcogen compound while improving the crystallinity.

Then, an organic coating layer forming step and a coating layer heat treating step may be performed. The chalcogen element, which is a member of the metal chalcogen compound, is highly volatile and may form a chalcogen deficient metal chalcogen compound in which the chalcogen element is insufficient in terms of the stoichiometric ratio in the light absorber formation step. Further, even in the subsequent heat treatment for improving the crystallinity of the light absorber, metal chalcogen compounds lacking chalcogen elements can be formed by volatilization of chalcogen elements, and defects due to hetero elements such as oxygen can be formed have. Defects present in the metal chalcogen compound can generate defect levels (energy levels due to defects) located between energy band gaps, which are caused by the recombination of photoelectrons and / Can be caused to disappear. Accordingly, by removing the defects of the metal chalcogen compound through the organic coating layer formation step and the coating layer heat treatment step, the solar cell efficiency can be improved.

As described above, in the solar cell manufactured by the manufacturing method according to one embodiment of the present invention, a metal chalcogen compound having a size of nano or quantum dots is formed on the surface (including pores) of the porous inorganic electron transport layer, It is very important to homogenize and uniformly supply the chalcogen source into the open pores without damaging or blocking the open pore structure since the pore of the porous inorganic electron transporting layer filled with the hole transporting material has a structure Do. In addition, it should be possible to prevent the formation of the second phase, such as chalcogen particles, by supplying the chalcogen source.

In this respect, a solution (organic solution) in which the chalcogen-containing organic material is dissolved and a chalcogen-containing organic material is used as the chalcogen source is applied to the porous inorganic electron transport layer in which the metal chalcogen compound is formed, And as a chalcogen source, it is possible to prevent damage to the open pore structure and to supply the chalcogen element uniformly and homogeneously, and by supplying the chalcogen element to the metal chalcogen compound using the chalcogen-containing organic coating layer, It is possible to effectively prevent generation of an abnormality such as a coenzyme particle.

In detail, in the step of forming an organic coating layer on a chalcogen by coating an organic material on a porous inorganic electron transport layer formed with a metal chalcogen compound, the chalcogen-containing organic material is a substance which satisfies the following Chemical Formula 1, Chemical Formula 2 or Chemical Formula 3 ≪ / RTI >

(Formula 1)

X is a chalcogen element, R ₁ and R ₂ are, independently of each other, -NR ₁₁ R ₁₂ , (C 1 -C 20) alkyl, (C 6 -C 20) aryl or (C 6 -C 20) C20) alkyl, and R < ₁₁ > and R < ₁₂ > are independently of each other hydrogen or (C1-C20) alkyl. Here, X may be S or Se.

(2)

In Formula (2), X is a chalcogen element, and R ₃ and R ₄ are independently of each other hydrogen or (C 1 -C 20) alkyl. Here, X may be S or Se.

(Formula 3)

이며, R₂₁은 (C1-C20) 알킬, (C6-C20) 아릴 또는 아미노이며, R₅는 수소 또는 (C1-C20)알킬이다. 이때, X는 S 또는 Se일 수 있다. X is a chalcogen element, n is an integer from 1 to 5, R is independently from each other hydrogen, halogen, (C1-C20) alkyl or

And, R ₂₁ is (C1-C20) alkyl, (C6-C20) aryl or amino, R ₅ is hydrogen or (C1-C20) alkyl. Here, X may be S or Se.

In Formulas 1 to 3, the alkyl of R ₁ , R ₂ , R ₃ , R ₄ or R ₅ includes hydroxyalkyl, and hydroxyalkyl may mean that the hydrogen of the alkyl is substituted with hydroxy, May mean that the terminal is substituted with hydroxy.

Specifically, the coating layer of the chalcogen-containing organic compound satisfying Chemical Formulas (1) to (3) can be thermally decomposed and removed by supplying a chalcogen element to the metal chalcogen compound through heat treatment.

이며, R₂₁은 (C1-C5) 알킬 또는 아미노이며, R₅는 수소 또는 (C1-C6)알킬인 것이 좋다.It is possible to easily and uniformly form a coating layer even in an electron transport layer in which fine pores exist and to effectively decompose at a low temperature where growth of metal chalcogen compounds of nano to quantum dot size is prevented, to not be damaged, in the formula 1 R ₁ and R ₂ are independently from each other, -NR ₁₁ R _12, (C1-C10) alkyl, (C6-C10) aryl or (C6-C12) aralkyl (C1-C10) R ₁₁ and R ₁₂ are independently hydrogen or (C 1 -C 10) alkyl. More preferably, R ₁ and R ₂ in the general formula (1) are, independently of each other, -NR ₁₁ R ₁₂ or a C1-C5) alkyl, R ₁₁ and R ₁₂ are each independently hydrogen or (C1-C5) alkyl. Also for the above-mentioned reason, in the general formula (2), R ₃ and R ₄ independently of one another are preferably hydrogen or (C 1 -C 5) alkyl. Also, for the above-mentioned reasons, n in the general formula (3) is an integer of 1 to 3, and Rs independently of one another are hydrogen, halogen, (C1-C5)

, R ₂₁ is (C 1 -C 5) alkyl or amino, and R ₅ is hydrogen or (C 1 -C 6) alkyl.

More preferably, the chalcogen-containing organic material may be selected from a substance which satisfies the following formula 1-1 or the following formula 1-2.

(1-1)

R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ independently of one another are hydrogen or (C 1 -C 20) alkyl, preferably R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ may be independently from each other, it may be hydrogen or (C1-C10) alkyl, and more preferably from R _31, R _32, R ₃₃ and R ₃₄ are independently of each other, hydrogen or (C1-C5) alkyl. Here, X may be S or Se.

(1-2)

R ₄₁ and R ₄₂ are independently hydrogen or (C 1 -C 20) alkyl and R ₄₃ is (C 1 -C 20) alkyl, preferably R ₄₁ and R ₄₂ are independently is hydrogen or (C1-C10) alkyl, R ₄₃ is (C1-C10) may be an alkyl, preferably from, R ₄₁ and R ₄₂ are independently hydrogen or (C1-C5) alkyl each other more, R ₄₃ May be (C1-C5) alkyl. Here, X may be S or Se.

Concretely, the chalcogen-containing organic material may be a substance which satisfies the general formulas (1) to (3) and has a melting point of 100 to 200 ° C. A chalcogen-containing organic material having a low melting point of 100 to 200 ° C is more effective in preventing pyrolysis of chalcogen-containing organic materials at a very low temperature and preventing staining due to organic substances remaining after heat treatment and contamination by organic substances.

As a practical, non-limiting example, the chalcogen-containing organics can be selected from the group consisting of thioacetamide, thiourea, thioacetic acid, thiophenol, selenourea, 1,1 -Dimethyl-2-selenourea) seleno acetamide, 2- [2-fluoro-4- [(5-hydroxypentyl) seleno] phenoxy] -).

In the method for producing a solar cell according to the present invention, the concentration of the chalcogen-containing organic substance in the organic solution may be 10 to 200 mg / mL. The organic material solution may contain a high concentration of chalcogen-containing organic material of 10 to 200 mg / mL, whereby a continuous coating layer can be stably formed. When the coating layer is heat-treated, a sufficient amount of metal It can supply the element of koza.

The solvent of the organic solution may be any solvent that dissolves the chalcogen-containing organic material and does not chemically react with the electron transport layer material. As a specific example, the solvent of the organic solution may be a non-aqueous polar organic solvent, and the solvent may be selected from the group consisting of gamma-butyrolactone, formamide, dimethylformamide, diformamide, acetonitrile, But are not limited to, furan, dimethyl sulfoxide, acetone,? -Terpineol,? -Terpineol, dihydrotherphenol, methanol, ethanol, propanol, butanol, pentanol, hexanol, chlorobenzene, - 1,2-dichlorobenzene, chloroform, acetonitrile, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), methyl ethyl ketone, Methyl n-propyl ketone, N-methylpyrrolidone (NMP), propylene carbornate, nitromethane, sulforane, ethylene (ethylene glycol) gl ycol), and hexamethylphophoramide (HMP).

Considering the structure of the porous inorganic electron transport layer having a porous structure, it is preferable that the coating of the solution in which the chalcogen-containing organic material is dissolved is performed through spin coating so that a uniform coating layer is formed even in a large area. However, May be used, and the present invention is not limited by the method of applying the organic solution.

The conditions of the spin coating may be appropriately controlled in consideration of the porosity and thickness of the porous inorganic electron transport layer. However, as described above, the thickness of the electron transport layer having a thickness of 0.1 to 5 탆 and a specific surface area of 10 to 100 m ² / , Spin coating may be performed to increase the rpm sequentially at low rpm to high rpm to more easily form a chalcogen-containing organic coating layer on the open pore surface of the porous inorganic electron transport layer. As a specific, non-limiting example, spin coating may be performed sequentially in the order of 800-1200 rpm and 1800-2500 rpm after a low rpm coating of 300-600 rpm is performed. As the organic solution which has not penetrated into the electron transport layer during spin coating is discharged to the outside, it is of course possible that the organic solution which can sufficiently wet the surface of the electron transport layer is applied.

After the organic solution is applied to form an organic coating layer on the electron transport layer in which the metal chalcogen compound is formed, heat treatment may be performed, and the chalcogen-containing organic coating layer may be thermally decomposed by heat treatment. It is possible to effectively pyrolyze the organic coating layer containing chalcogen and to heal defects due to chalcogen deficiency of chalcogen-deficient metal chalcogen compounds through the supply of chalcogen elements and to improve the particle size of metal chalcogen compounds of nano- To prevent the change, the heat treatment of the organic coating layer can be performed at a temperature of 150 to 350 DEG C in an inert atmosphere (atmosphere of one or more selected gases in helium, neon, argon and nitrogen).

The step of forming the hole transport layer is a step of impregnating a solution containing the hole conductive organic material so as to fill the void existing in the porous electron transport layer and cover the upper part of the porous electron transport layer. The impregnation is preferably carried out by spin coating. The thickness of the hole-transporting organic material covering the electron-transporting layer with respect to the uppermost portion of the electron-transporting layer is preferably 30 nm to 200 nm.

The hole-conducting organic material may be a single-molecule or high-molecular organic material ordinarily used in the field of organic solar cells that conducts holes. Preferably, the hole-conducting organic material is a polymeric organic material such as thiophene, paraphenylene vinylene, carbazole, One or two or more can be selected. The thiophene-based compound is more preferable in terms of energy matching with the metal chalcogen compound.

In detail, the hole-conducting organic material is selected from the group consisting of P3HT (poly [3-hexylthiophene]), MDMO-PPV (poly [2-methoxy- 5- (3 ', 7'- dimethyloctyloxyl) (3-octyl thiophene), POT (poly (octyl thiophene)), P3DT (poly (2-methoxy-5- 3-decyl thiophene), poly (3-dodecyl thiophene), poly (p-phenylene vinylene), poly (9,9'-dioctylfluorene-co- ), Polyaniline, Spiro-MeOTAD ([2,22 ', 7,77'-tetrkis ( N, Ndi- p -methoxyphenyl amine) -9,9,9'- spirobi fluorine]), CuSCN, CuI, PCPDTBT (Poly [2,1,3-benzothiadiazole-4,7-diyl4,4-bis (2-ethylhexyl-4H-cyclopenta [ dl]], Si-PCPDTBT (poly [(4,4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'- 2,1,3-benzothiadiazole) -4,7-diyl]), PBDTTPD (poly ((4,8-diethylhexyloxyl) benzo [1,2- b: 4,5-b '] dithiophene) -1,3-diyl)), PFDTBT (poly [2,7- (9- (2-ethylhexyl) ) -9-hex yl-fluorene) -tallow-5,5- (4 ', 7-di-2-thienyl-2', 1'3'-benzothiadiazole)], PFO-DBT (poly [ 5 '- (4', 7'-di-2-thienyl-2 ', 1', 3'-benzothiadiazole)], PSiFDTBT (poly [ (4,7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5,5'-diyl], PSBTBT (poly [ 4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silole) -2,6-diyl-6- (2,1,3-benzothiadiazole) diyl]), PCDTBT (Poly [[9- (1-octylononyl) -9H-carbazole-2,7-diyl] -2,5-thiophenediyl-2,1,3-benzothiadiazole- 5-thiophenediyl], PFB (poly (9,9'-dioctylfluorene-co-bis (N, N '- (4, Poly (3,4-ethylenedioxythiophene), PEDOT: PSS poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate), PTAA (poly (triarylamine) ), Poly (4-butylphenyl-diphenyl-amine), and copolymers thereof.

Here, the hole transport layer may have a laminated structure of different hole conductive organic materials in terms of improving the bonding force and / or energy matching between the second electrode and the hole transport layer.

The solvent used for forming the hole transport layer may be a solvent in which the hole conductive organic material is dissolved and does not chemically react with the metal chalcogen compound and the substance of the electron transport layer. For example, the solvent used to form the hole transport layer can be a nonpolar solvent and can be, for example, toluene, chloroform, chlorobenzene, dichlorobenzene, anisole, xylene, and a hydrocarbon-based solvent having 6 to 14 carbon atoms.

The second electrode is a counter electrode of the first electrode located under the electron transport layer, and may be a metal electrode ordinarily used in the field of solar cells. As a practical example, the second electrode may be one or more selected from gold, silver, platinum, palladium, copper, aluminum, carbon, cobalt sulfide, copper sulfide, nickel oxide and combinations thereof. The second electrode may be fabricated by physical vapor deposition, chemical vapor deposition, or thermal evaporation.

Hereinafter, an actual production example of a solar cell will be described. However, it should be understood that the present invention is not limited to the illustrated embodiments, but is merely an example of the present invention in order to facilitate an overall understanding of the present invention.

(Example 1)

A glass substrate (FTO: F-doped SnO ₂ , 8 ohms / sq, Pilkington, hereinafter referred to as FTO substrate) coated with fluorine-containing tin oxide (first electrode) was cut into a size of 25 x 25 mm, FTO was partially removed.

TiO ₂ thin films of about 50 nm thick as a recombination preventive film were prepared by spray pyrolysis on cut and partially etched FTO substrates.

TiO ₂ powder having an average particle size of 60 nm (manufactured by hydrothermally treating titanium perocomplex aqueous solution having 1 wt% based on TiO ₂ dissolved therein at 250 ° C. for 12 hours) was dissolved in ethyl alcohol in an amount of 10% by weight of ethyl cellulose 5 ml per 1 g of TiO ₂ was added, terpinol (5 g) per 1 g of TiO ₂ was added and mixed, and ethyl alcohol was removed by vacuum distillation to prepare a TiO ₂ paste.

The TiO ₂ paste prepared by the above method was coated on a FTO substrate coated with a TiO ₂ thin film having a dense structure of about 50 nm thick by screen printing and heat-treated at 500 ° C. for 2 hours to form a porous thin film . After the temperature of the substrate dropped to room temperature, ultraviolet / ozone treatment (UV / ozone treatment) was performed for about 5 minutes in order to increase the wettability of the organic residue and the substrate used in the paste which might remain on the substrate. Subsequently, the substrate was immersed in a 40 mM aqueous solution of TiCl ₄ maintained at 60 ° C., immersed in the substrate for about 1 hour, washed with deionized water and ethanol, dried, and then heat-treated at 500 ° C. for 30 minutes.

To attach the Sb ₂ S ₃ light absorber to the prepared porous TiO ₂ thin film (porous inorganic electron transport layer), 0.65 g of SbCl ₃ (manufactured by Aldrich) was added to 2.5 mL of acetone to obtain a solution of the dissolved first precursor and 25 mL of ion-exchanged _{Na 2 S 2 O 3 (Aldrich} ) 3.95g was dissolved claim then a solution of the precursor solution was again prepared mixed solution was added 72.5 mL of ion-exchanged water and uniformly. The substrate with the porous TiO ₂ thin film (porous inorganic electron transport layer) formed thereon was immersed in the prepared mixed solution and allowed to stand at a temperature of 5 ° C or lower for 2 hours to form amorphous Sb ₂ S ₃ light To form an absorber. The formed Sb ₂ S ₃ was heat-treated at 300 ° C for 5 minutes in an Ar atmosphere.

Thioacetamide (Aldrich), an organosulfur compounds, was dissolved in NN-dimethylformamide (DMF, Aldrich) at a concentration of 100 mg / mL on a porous electron transport layer on which a light absorber was formed The organic solution was spin-coated at 2000 rpm for 100 seconds to form an organic coating layer.

After the spin coating, the substrate was heat-treated at 300 캜 for 5 minutes in an Ar atmosphere, and the surface treatment of Sb ₂ S ₃ produced on the surface of the porous electron transport layer was performed by solution bath growth (chemical bath deposition). As a result of XPS analysis of Sb ₂ S ₃ produced through surface treatment after thermo-decomposing the thioacetamide solution, other elements that can form defects such as O, except Sb and S, are found (See TA treatment in Fig. 2).

(2, 6- (4,4-bis- (2-ethylhexyl) -4H-cyclopenta [2,1-b ; 3,4-b '] dithiophene-alt-4,7 (2,1,3-benzothioadiazole), 1-material] was dissolved in 1,2-dichlorebenzene at 5 mg / mL Was spin-coated at 2000 rpm for 100 seconds to fill the pores of the porous electron transport layer with PCPDTBT and cover the top of the porous electron transport layer with PCPDTBT. Then, PEDOT: PSS [poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate)] was again deposited by spin coating such as PCPDTBT. After the spin coating, Au was vacuum deposited on the upper portion of the hole transporting layer by a thermal evaporator (not more than 5 x 10 ^-6 torr) to form an Au electrode having a thickness of about 90 nm. After the electrode deposition, the solar cell was fabricated by heat treatment in an Ar atmosphere at 120 ° C for 30 minutes.

(Example 2)

In Example 1, after preparing a porous electron transport layer having a light absorber, thiourea (Aldrich) was dissolved in N, N-dimethylformamide (N, N-dimethylformamide) as organosulfur compounds for surface treatment of the light absorber , N-Dimethylformamide, DMF, Aldrich) at a concentration of 100 mg / mL. As a result of XPS analysis of Sb ₂ S ₃ produced through surface treatment after applying a thiourea solution, other elements capable of forming defects such as O, except Sb and S, can be found (See TO treatment in Fig. 2).

(Comparative Example)

A comparative solar cell was prepared in the same manner as in Example 1 except that a porous electron transport layer having a light absorber was formed, and then a hole transport layer was directly formed without using surface treatment using thioacetamide. Sb ₂ S ₃ prepared by the method of this comparative example was analyzed by XPS to find that Sb and S contained a large amount of elements capable of forming defects such as O (see NO treatment in FIG. 2).

In order to measure the current-voltage characteristics of the solar cells manufactured in Examples 1, 2 and Comparative Example, an artificial solar device (ORIEL class A solar simulator, Newport, model 91195A) and a source- Ketley model 2420) and external quantum efficiency (EQE) were measured using a 300 W Xenon lamp (Newport), a monochromator (Newport cornerstone 260) and a multi-meter (Kethley model 2002) The cell characteristics of Example 1 and Comparative Example are shown in FIG.

All the measured values were obtained by measuring four devices manufactured by the same device five times and then averaging them.

The solar cells manufactured in Example 1 and Example 2 have similar current-voltage characteristics and have an energy conversion efficiency of 7% or more at a light amount of 100 mW / cm ² , and the conversion efficiency the conversion efficiency of the solar cell manufactured in the comparative example was less than 6% and the efficiency was low.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (10)

a) forming a porous inorganic electron transporting layer;
b) forming a metal chalcogen compound as a light absorber on the surface of the porous inorganic electron transporting layer;
c) forming a chalcogen-containing organic coating layer by applying a solution in which a chalcogen-containing organic material is dissolved in a porous inorganic electron transport layer formed with a metal chalcogen compound;
d) heat treating the chalcogen-containing organic coating layer; And
e) forming a hole transporting layer by applying a hole transporting organic material on the porous inorganic electron transporting layer;
Wherein the method comprises the steps of: The method according to claim 1,
The metal chalcogen compound may be selected from the group consisting of Fe, Co, Ni, Cu, Mo, Cd, Ga, In, Sn, A method for producing a solar cell which is a chalcogen compound of at least one selected from the group consisting of lead (Pb), antimony (Sb) and bismuth (Bi) The method according to claim 1,
Wherein the chalcogen-containing organic material is selected from materials satisfying the following Chemical Formulas (1) to (3).
(Formula 1)

(In formula 1, X is a knife kojen element, R ₁ and R ₂ are independently from each _{other, -NR 11 R 12, (C1} -C20) alkyl, (C6-C20) aryl or (C6-C20) aralkyl (C1 And R < ₁₁ > and R < ₁₂ > are independently of each other hydrogen or (C1-C20)
(2)

(Wherein X is a chalcogen element and R ₃ and R ₄ are independently of each other hydrogen or (C 1 -C 20) alkyl)
(Formula 3)

Wherein X is a chalcogen element, n is an integer from 1 to 5, and R is independently from each other hydrogen, halogen, (C1-C20) alkyl or

And, R ₂₁ is (C1-C20) alkyl, (C6-C20) aryl or amino, R ₅ is hydrogen or (C1-C20) alkyl) The method of claim 3,
Wherein the chalcogen-containing organic material is selected from a material satisfying the following Formula 1-1 or Formula 1-2.
(1-1)

(Wherein X is a chalcogen element and R ₃₁ , R ₃₂ , R ₃₃ and R ₃₄ are, independently from each other, hydrogen or (C 1 -C 20) alkyl)
(1-2)

(Wherein, X is a chalcogen element, R ₄₁ and R ₄₂ are independently of each other hydrogen or (C 1 -C 20) alkyl, and R ₄₃ is (C 1 -C 20) alkyl) The method according to claim 1,
Wherein the concentration of the chalcogen-containing organic material in the solution is 10 to 200 mg / mL. The method according to claim 1,
Wherein the chalcogen-containing organic coating layer is thermally decomposed by the heat treatment. The method according to claim 1,
Wherein the heat treatment is performed at 150 to 350 占 폚 in an inert atmosphere. The method according to claim 1,
Step b) is a chemical bath deposition method (CBD); And a successive ionic layer adsorption and reaction method (SILAR). The method according to claim 1,
After the step b), the porous inorganic electron-transporting layer on which the light absorber is formed is further subjected to a heat treatment at a temperature of 200 to 400 캜 in an inert atmosphere. A solar cell produced by the method of any one of claims 1 to 9.

Images