KR102553726B1 - A solar cell having a hole transport layer containing a metal oxide - Google Patents

Abstract

The present invention relates to a solar cell having enhanced open-circuit voltage and high device photoelectric conversion efficiency, comprising: a first electrode and a second electrode disposed to face each other; a photoactive layer positioned between the first and second electrodes; and a hole transport layer positioned between the second electrode and the photoactive layer, wherein the photoactive layer includes an organic material or a perovskite material, and the hole transport layer includes a metal oxide and a dipole material. A solar cell and a method for manufacturing the same are provided.

Description

A solar cell having a hole transport layer containing a metal oxide}

The present invention relates to a high-efficiency organic solar cell and a perovskite solar cell using a metal oxide as a hole transport layer.

A solar cell is a device capable of converting solar energy into electrical energy by applying a photovoltaic effect. Solar cells can be divided into inorganic solar cells and organic solar cells according to the materials constituting the photoactive layer among internal components. Among them, in the organic solar cell, the photoactive layer is composed of organic semiconductor materials such as single molecules or polymers, and the photoactive layer is composed of electron donors and electron acceptors. Recently, a bulk heterojunction (BHJ) photoactive layer in which an electron donor and an electron acceptor are mixed with each other has been developed and used. Fullerene-based compounds, which are conventional electron acceptor materials, have problems such as low absorption in the visible light region and low thermal stability. Accordingly, non-fullerene-based electron acceptor materials, such as Y6 (BTP-4F), have been recently developed, and electron donor materials optimized therefor, such as PBDB-T, PM6, and PM7, have been developed. developed and used in combination with each other.

In order to achieve high photoelectric conversion efficiency and excellent stability in an organic solar cell, it is essential to use a hole transport layer having excellent characteristics as well as a combination of an electron donor and an electron acceptor. That is, it is necessary to develop a material having high light transmittance in the solar spectrum, high charge mobility, and high atmospheric and moisture stability. PEDOT:PSS has high hole conductivity and high transmittance, so it is mainly used in the hole transport layer of organic solar cells. In order to solve the problem of the hole transport layer, studies are being conducted on effective hole transport using inorganic oxides and improving device performance and device stability. However, inorganic oxides reported so far have a low open circuit voltage (Voc) despite having a deeper valence band than PEDOT:PSS. Therefore, it is essential to develop a stable hole transport material that can replace PEDOT:PSS and maximize open-circuit voltage.

Recently, in order to overcome the oxygen and moisture instability of organic materials, many research results have been reported on the use of p-type metal oxides, which have excellent chemical stability compared to organic materials, as hole transport materials for organic solar cells. For example, nickel oxide (NiO) is a metal oxide that is chemically stable in the air and has a wide band gap. It has advantages. In addition, since it has high optical transmittance and high electrical hole mobility, excellent properties as a hole transport material can be expected. Nickel oxide is being studied not only for organic solar cells but also for excellent properties as a hole transport layer for perovskite solar cells using ABX _3- type organic-inorganic composite perovskite materials as photoactive layers, so many studies are being conducted. .

However, unlike when the hole transport layer made of metal oxide is applied to the fullerene-based photoactive layer, when applied to the non-fullerene-based photoactive layer, the open-circuit voltage has a lower value than that of PEDOT:PSS. For example, when nickel oxide is used as a hole transport layer, the open-circuit voltage is less than 0.80 V, which is lower than that of PEDOT:PSS, which has a value of 0.80 V or more. As a result, the efficiency of organic solar cells using nickel oxide as a hole transport layer remains at about 10%. Therefore, it is necessary to solve these problems in order to improve the efficiency of solar cells.

Korean Patent Publication 10-2018-0106894

The present invention is intended to solve the conventional problems, and aims to implement a high-efficiency organic solar cell and a perovskite solar cell by adjusting the energy level by introducing a dipole material into a metal oxide used as a hole transport material and using the same to be

However, these tasks are illustrative, and the scope of the present invention is not limited thereby.

According to one aspect of the present invention for solving the above problems, the first electrode and the second electrode disposed to face each other; a photoactive layer positioned between the first and second electrodes; and a hole transport layer positioned between the second electrode and the photoactive layer, wherein the photoactive layer includes an organic material or a perovskite material, and the hole transport layer includes a metal oxide and a dipole material. A solar cell is provided.

According to an embodiment of the present invention, the hole transport layer may be a single layer in which a metal oxide and a dipole material are mixed with each other.

According to one embodiment of the present invention, the hole transport layer may have a two-layer structure composed of a metal oxide and a dipole material layer formed thereon.

According to one embodiment of the present invention, the dipole material may include a sulfonic acid salt.

According to one embodiment of the present invention, the sulfonic acid salt may include a hydroquinone sulfonic acid salt.

According to one embodiment of the present invention, the hole transport layer may have a thickness ranging from 1 to 50 nm.

According to one embodiment of the present invention, the photoactive layer made of the organic material may have a two-layer structure in which an electron donor and an electron acceptor form a p-n junction.

According to one embodiment of the present invention, the photoactive layer made of the organic material may have a bulk heterojunction structure made of an electron donor and an electron acceptor.

According to one embodiment of the present invention, the organic material may include a fullerene-based organic material or a non-fullerene-based organic material. The non-fullerene-based organic material may include at least one selected from the group consisting of IDT-Br, ITIC, and Y6.

According to another aspect of the present invention, a solar cell manufacturing method comprising forming a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode on one surface of a substrate, wherein the photoactive layer is made of an organic material A method for manufacturing a solar cell is provided, which includes forming a hole transport layer including or including a perovskite material and including a metal oxide and a dipole material on top of the first electrode.

According to an embodiment of the present invention, the forming of the hole transport layer may include a single layer in which a metal oxide and a dipole material are mixed with each other.

According to one embodiment of the present invention, the forming of the hole transport layer may include a two-layer structure including a metal oxide layer and a dipole material layer formed on the metal oxide layer.

According to one embodiment of the present invention, the dipole material may include a sulfonic acid salt, and the sulfonic acid salt may include a hydroquinone sulfonic acid salt.

According to one embodiment of the present invention, the method of forming the hole transport layer may be performed by a wet coating/spin coating method using a metal oxide precursor solution and a sulfonic acid salt solution in which a metal oxide precursor solution is mixed. can

According to one embodiment of the present invention, the forming of the hole transport layer may include forming a metal oxide layer by a wet coating method using a metal oxide precursor solution; and forming a sulfonic acid salt layer on top of the metal oxide layer by a wet coating method using a sulfonic acid salt solution.

According to one embodiment of the present invention, the metal oxide precursor solution may be a solution of at least one selected from the group consisting of nickel acetate tetrahydrate, nickel acetylacetonate, nickel nitrate hexahydrate, nickel formate dihydrate, nickel chloride hydrate, and nickel ethylhexanoate. .

According to one embodiment of the present invention, the sulfonic acid salt solution may be a solution of the hydroquinone sulfonic acid salt.

According to one embodiment of the present invention made as described above, by using a metal oxide and a dipole material together as a hole transport layer of an organic solar cell or a perovskite solar cell, improved open-circuit voltage and high device photoelectric conversion compared to the prior art efficiency can be achieved. Of course, the scope of the present invention is not limited by these effects.

1 is a schematic diagram of a structure of an organic solar cell.
2 is an X-ray diffraction analysis result of hole transport layers according to Examples and Comparative Examples of the present invention.
Figure 3 is a result of measuring the transmittance (Transmittance) according to the optical wavelength (wavelength) of the hole transport layer according to Examples and Comparative Examples of the present invention.
4 is a result of component analysis of hole transport layers according to Examples and Comparative Examples of the present invention by X-ray photoelectron spectroscopy (XPS).
5 is an analysis result of the hole transport layer according to Examples and Comparative Examples of the hole transport characteristics of the present invention.
6 is a result of measuring the hole transport layer according to Examples and Comparative Examples of the present invention by UPS (Ultraviolet Photoelectron Spectroscopy).
7 shows a current density (J)-voltage (V) graph result of an organic solar cell according to an embodiment of the present invention.
8 illustrates stability test results of an organic solar cell according to an embodiment of the present invention.
9 shows energy levels of hole transport layers according to Examples and Comparative Examples of the present invention.
10 shows energy levels at the interface between the hole transport layer and the photoactive layer.
11 illustrates current density (J)-voltage (V) graph results of organic solar cells according to Examples and Comparative Examples of the present invention.
12 to 13 show current density (J)-voltage (V) graph results of perovskite solar cells according to Examples and Comparative Examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail, with reference to accompanying flow charts illustrating, by way of example, specific production examples in which the present invention may be practiced. These preparation examples are described in sufficient detail to enable one skilled in the art to practice the present invention. It should be understood that the various preparations of the present invention are different, but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be embodied in one manufacturing example in another manufacturing example without departing from the spirit and scope of the present invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed manufacturing example may be changed without departing from the spirit and scope of the invention. Accordingly, the detailed description set forth below is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is limited only by the appended claims, along with all equivalents as claimed by those claims. Similar reference numerals in the drawings indicate the same or similar functions in various aspects, and the length, area, thickness, and the like may be exaggerated for convenience.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention.

1 is a schematic view of the structure of an organic solar cell 1 according to the present invention. As shown in FIG. 1, the organic solar cell 1 according to the present invention includes a first electrode 100 and a second electrode 200 disposed to face each other, and the first and second electrodes 100 and 200 ) It includes a photoactive layer 500, a hole transport layer 300 and an electron transport layer 400 located between.

The first electrode 100 according to the present invention, for example, as shown in FIG. 1, may be located in the direction of the incident sunlight, and the second electrode 200 is larger than the first electrode 100. It may be located on the far side of the relatively incident sunlight direction. In one example, the first electrode 100 may be a transparent electrode. The type of the first electrode may be, for example, a metal oxide such as zinc oxide, indium oxide, indium tin oxide (ITO) or indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al or SnO ₂ :Sb; Conductive polymers such as PEDOT:PSS, polypyrrole, or polyaniline may be exemplified, but are not limited thereto.

The first electrode 100 may be formed on the substrate 600, for example. The substrate 600 may be a glass substrate or a transparent plastic substrate. The plastic substrate may be, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyimide (PI) or triacetyl cellulose (TAC), but is not limited thereto no.

The organic solar cell 1 of the present invention includes a second electrode 200 disposed to face the first electrode 100. The second electrode 200 includes, for example, a metal material such as gold, silver, aluminum, or copper.

The photoactive layer 500 is made of an organic material in which excitons are formed when sunlight is applied thereto. For example, such a photoactive layer is composed of an organic material, and may have a bi-layer structure in which an electron donor and an electron acceptor are formed of a p-n junction. Alternatively, as another example, it may have a bulk-heterojunction (BHJ) structure in which an electron donor and an electron acceptor are mixed.

The electron donor includes at least one of a polymer and a small molecule. The polymer material is poly-3-hexylthiophene (P3HT), Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b ´]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}); It may include one or more selected from the group consisting of PTB7, PCE10, PM6 and PM7.

The electron acceptor includes a fullerene-based or non-fullerene material. The fullerene-based electron acceptor may include one or more selected from the group consisting of PC60BM, PC70BM, ICBA, and C60. The non-fullerene-based electron acceptor may include one or more selected from the group consisting of IDT-Br, ITIC, and Y6.

The hole transport layer 300 is positioned on the first electrode 100 described above and serves to facilitate hole movement to the first electrode 100 . According to the technical idea of the present invention, the hole transport layer 300 is composed of a metal oxide and a dipole material. This dipole material exists at least on the surface of the metal oxide, and due to this dipole material, a change in energy level occurs at the interface with the photoactive layer 500 stacked on top of the hole transport layer 300.

Metal oxides include nickel oxide, titanium oxide, zinc oxide, copper oxide, chromium oxide, tin oxide, silver oxide, manganese oxide, tungsten oxide, vanadium oxide, copper-doped nickel oxide, silver-doped nickel oxide, magnesium-doped nickel oxide , calcium doped nickel oxide, strontium doped nickel oxide, barium doped nickel oxide, aluminum doped nickel oxide, cobalt doped nickel oxide, cesium doped nickel oxide, iron doped nickel oxide, lanthanum doped nickel oxide, At least one selected from the group consisting of lithium-doped nickel oxide and zinc-doped nickel oxide may be used.

As described above, these metal oxides have the advantages of excellent chemical stability, high light transmittance, and high hole mobility, but when nickel oxide is applied to a non-fullerene-based bulk double junction material, the open circuit voltage is used as a conventional hole transport layer. There is a problem that it is significantly lower than that of PEDOT:PSS. For this reason, although the valence band (VB) of nickel oxide is deep, it seems that the Fermi level is located high.

In order to solve this problem, the present inventors used a dipole material together with the metal oxide as a hole transport layer, and through this, the problem of low open circuit voltage and efficiency could be solved. The hole transport layer may be made of a single layer in which a metal oxide and a dipole material are mixed, or a two-layer structure in which a metal oxide layer and a dipole material layer are formed as separate layers.

Such dipole materials may include, for example, salts of sulfonic acids. Among the sulfonic acid salts, the negatively charged substance is a substance with a -1 charge composed of RSO ₃ ^- , and the positively charged substance is Li, Na, K, Rb, Cs with a +1 charge. , alkali metals such as Fr.

The sulfonic acid salt may be, for example, a hydroquinone sulfonic acid salt represented by Formula 1 below.

<Formula 1>

(In the formula, M ⁺ represents a cation.)

In this case, M ⁺ may be any one of lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, and francium ion, but is not limited thereto.

According to the technical concept of the present invention, when a metal oxide and a sulfonic acid salt are used together as a hole transport layer, the dipole characteristics of SO ₃ ^- and M ⁺ contained in the sulfonic acid salt control the energy level and surface composition of the metal oxide to move the vacuum level ( By causing a vacuum level shift), hole transfer at the interface of the hole transport layer can be improved, and through this, an effect of increasing the open circuit voltage can be exhibited.

The method of forming the hole transport layer is not particularly limited, but a wet process using a solution such as sol-gel or spin coating, or atomic layer deposition, It can be manufactured by various process methods such as pulsed laser deposition, sputtering, evaporation, chemical vapor deposition, electrochemical plating, spray coating, and thermal decomposition.

For example, in the case of using a wet process, a mixed solution is prepared by adding a sulfonic acid salt solution in which a sulfonic acid salt is dissolved to a metal oxide precursor solution in which a metal oxide is dissolved, and then spin-coating using the mixed solution to form a single-layer hole transport layer. can form Alternatively, a metal oxide layer may be first formed using a metal oxide precursor solution, and then a sulfonate thin film layer may be separately formed on the metal oxide layer using a sulfonate solution.

Hereinafter, nickel oxide as a metal oxide and sulfonic acid salt as a dipole material will be described as an example as an example, but the technical idea of the present invention is not limited thereto.

In the case of nickel oxide, at least one selected from the group consisting of nickel acetate tetrahydrate, nickel acetylacetonate, nickel nitrate hexahydrate, nickel formate dihydrate, nickel chloride hydrate, and nickel ethylhexanoate may be used as the nickel oxide precursor solution. In addition, the solvent may include an alcohol-based organic solvent such as 2-methoxyethanol, ethanol, or isopropanol. These metal oxide precursor solutions may range from 0.01 to 0.50 M.

A sulfonic acid salt solution can be prepared by dissolving the hydroquinone sulfonic acid salt represented by Formula 1 in an alcohol-based organic solvent such as 2-Methoxyethanol, ethanol, or isopropanol. Such sulfonic acid salt solutions may range from 0.001 to 0.050 M.

The hole transport layer may be formed to a thickness of 1 to 50 nm. If it is less than 1 nm, it cannot flatten the roughness of the surface of the ITO electrode and cannot function as a hole transport layer, and if it exceeds 50 nm, hole transport may be hindered because the salt has insulating properties.

In addition, the hole transport layer according to the technical idea of the present invention can be equally applied to perovskite solar cells. The basic structure of the perovskite solar cell is also substantially the same as the structure shown in FIG. 1, except that the photoactive layer is made of a perovskite material. The perovskite material may include an ABX ₃ type organic/inorganic composite perovskite material, for example, CH ₃ NH ₃ PbI ₃ . Even in the case of a perovskite solar cell, when a hole transport layer according to the technical concept of the present invention is applied, the photoelectric conversion efficiency of the solar cell can be increased.

Hereinafter, preparation examples and experimental examples of an organic solar cell and perovskite will be described to aid understanding of the present invention. However, the following preparation examples are only to aid understanding of the present invention, and the present invention is not limited to the preparation examples and experimental examples below.

<Manufacture of nickel oxide hole transport layer>

Nickel acetate tetrahydrate, a precursor of nickel oxide, is dissolved in 2-methoxyethanol at a concentration of 0.05M. Thereafter, 10uL of hydrochloric acid was added and dissolved at 100° C. for 12 hours to obtain a yellow nickel oxide precursor solution.

On the other hand, hydroquinone sulfonic acid potassium salt and hydroquinone sulfonic acid sodium salt are added to 2-methoxyethanol at a concentration of 0.005M, respectively, and then dissolved at 60 ° C for 12 hours to obtain a transparent solution got For convenience, a solution in which hydroquinone sulfonic acid potassium salt is dissolved is referred to as a sulfonic acid potassium salt solution, and a solution in which hydroquinone sulfonic acid sodium salt is dissolved is referred to as a sulfonic acid sodium salt solution.

Next, a nickel oxide mixed precursor solution for preparing a hole transport layer was prepared by mixing the hydroquinone sulfonate potassium salt solution or the hydroquinone sulfonate sodium salt solution with the nickel oxide precursor solution. The added sulfonic acid potassium salt solution or sulfonic acid sodium salt solution was 1, 2, 4 and 8% in terms of volume ratio (vol%) with respect to the nickel oxide precursor solution.

Using the prepared nickel oxide mixed precursor solution, a glass substrate was coated to a thickness of 15 nm by spin coating and heat treated at 300° C. for 30 minutes to prepare a nickel oxide layer applied as a hole transport layer. Hereinafter, nickel oxide prepared by adding a potassium sulfonate salt solution is expressed as NiO:K, and nickel oxide prepared by adding a sodium sulfonate salt solution is expressed as NiO:Na.

Meanwhile, as a comparative example, a nickel oxide precursor solution was spin-coated under the same conditions to form nickel oxide, which is denoted as NiO.

When NiO:K and NiO:Na used in the analysis of FIGS. 2 to 5 were mixed, the volume ratios of the potassium sulfonic acid salt solution and the sodium sulfonic acid salt solution were 2% and 1%, respectively.

2 shows the results of X-ray diffraction analysis of NiO:K, NiO:Na and NiO. Referring to FIG. 2, cubic octahedral peaks of nickel oxide were detected in all specimens, and it was confirmed that nickel oxide was formed under all manufacturing conditions.

3 shows the results of measuring the transmittance of NiO:K, NiO:Na, and NiO according to the wavelength of light. Referring to FIG. 3, it can be confirmed that all specimens exhibit high transmittance in the visible light region.

4 shows the results of component analysis of the surfaces of NiO:K, NiO:Na, and NiO by XPS. Referring to FIG. 4, in the case of NiO:K, potassium (K) and sulfur (S) were detected on the surface, and in the case of NiO:Na, sodium (Na) and sulfur (S) were detected on the surface. On the other hand, no elements among potassium, sodium and sulfur were detected in NiO. The detection of potassium and sulfur or the detection of sodium and sulfur makes it inferred that potassium or sodium and sulfur-containing sulfonic acid groups are present in the form of dipoles having positive and negative charges, respectively, on the surface of the nickel oxide layer. The presence of dipoles on the surface of nickel oxide contributes to improving the characteristics of solar cells, which will be described in detail later.

5 shows the results of analyzing the electrical conductivity of NiO:K, NiO:Na and NiO. Referring to FIG. 5, it was analyzed that NiO:K and NiO:Na had slightly lower electrical resistance and slightly higher conductivity than NiO.

6 shows UPS (Ultraviolet Photoelectron Spectroscopy) measurement results of NiO:K, NiO:Na, and NiO. NiO:K and NiO:Na not only confirm that E _F (fermi level) representing the work function is formed deeper by about 0.10 ~ 0.15 eV compared to NiO, but also has p-type characteristics (p-type property) (E _F - VB), it was also confirmed that NiO:K and NiO:Na showed relatively small values compared to NiO and exhibited stronger p-type properties.

Table 1 shows the results of the energy levels of NiO:K, NiO:Na and NiO. The cut-off in Table 1 is a value obtained through the secondary electron cut-off position of the UPS spectra, and through this, 21.22 (He energy)-E _cutoff = E _F was calculated represents a value. In addition, VB was calculated through the valence band edge position (= E _F -VB). E _F represents the Fermi energy level, and VB and CB represent the valence band level and the conduction band level, respectively.

hole transport layer
Cut-off (eV) E _F E _F -VB (eV) VB (eV) CB (eV) Comparative Example 2 (NiO) 16.72 4.48 0.88 5.36 1.23
Example 1 (NiO:K) 16.57 4.63 0.77 5.40 1.27
Example 2 (NiO:Na) 16.58 4.62 0.79 5.41 1.28

<Production of organic solar cells>

The organic solar cell device was fabricated in the structure of ITO/NiO/PM6:Y6-BO-4F/PFN-Br/Al. For the mixed solution for preparing the photoactive layer, 22mg of PM6 and Y6-BO-4F were added to 1mL of chlorobenzene at a ratio of 1:1, and then dissolved at 60°C for 4 hours. A solution for preparing the electron transport layer was prepared by dissolving 0.5 mg of PFN-Br in 1 mL of methanol at room temperature for 15 minutes.

A glass substrate patterned with indium tin oxide (ITO), a transparent electrode on one side, was washed with distilled water, acetone, and isopropanol, and UV-Ozone treatment was performed for 30 minutes. Next, a hole transport layer was formed by coating to a thickness of 15 nm by spin coating using the nickel oxide mixed precursor solution prepared by the above-described method and heat-treating at 300° C. for 30 minutes. Next, the mixed solution for preparing the photoactive layer was spin-coated at 2000 rpm for 30 seconds and heat-treated at 80° C. for 10 minutes to form a photoactive layer. Next, the electron transport layer was prepared by spin-coating at 5000 rpm for 30 seconds with the solution for preparing the electron transport layer, and then Al was formed thereon to a thickness of 100 nm as an electrode to complete device fabrication. Here, the case where NiO:K was used as the hole transport layer is referred to as Example 1, and the case where NiO:Na was used is referred to as Example 2. Meanwhile, as a comparative example, an organic solar cell was manufactured in the same manner as in Example 1 except for the hole transport layer. Comparative Example 1 was formed using PEDOT:PSS as a hole transport layer, and Comparative Example 2 used nickel oxide using the above-described nickel oxide precursor solution as a hole transport layer.

The current density-voltage characteristics (current density-Voltage (J-V)) of the organic solar cell according to the above Examples and Comparative Examples were measured and shown in FIG. 7, and the efficiency is shown in Table 2 below.

hole transport layer
open voltage
[V] short circuit current
[mA cm ^-2 ] Fill Factor maximum efficiency
[%] average efficiency
[%] Comparative Example 1 (PEDOT:PSS) 0.85 22.53 0.72 13.73 13.42 ± 0.3 Comparative Example 2 (NiO) 0.79 22.77 0.68 12.19 11.75 ± 0.4
Example 1 (NiO:K) 0.86 22.46 0.73 14.19 13.88 ± 0.3
Example 2 (NiO:Na) 0.85 22.31 0.74 13.95 13.72 ± 0.3

Referring to Table 2 and FIG. 7, Examples 1 and 2 using nickel oxide to which a sulfonic acid salt was added as a hole transport layer showed a higher open-circuit voltage than Comparative Example 2 using only nickel oxide, and PEDOT:PSS The same or higher open-circuit voltage was also shown for Comparative Example 1 used. In addition, it was confirmed that the average efficiency and maximum efficiency of Examples 1 and 2 exhibited better values than Comparative Examples 1 and 2. In the case of the examples, the maximum efficiency was as high as about 14%.

Stability test results of organic solar cells according to Examples and Comparative Examples are shown in FIG. 8 and Table 3. Examples 1 and 2 both showed excellent stability compared to Comparative Examples 1 and 2, and in particular, showed significantly higher stability than Comparative Example 1 (PEDOT:PSS), which is an organic material.

hole transport layer Stability after 50 days (%) Comparative Example 1 (PEDOT:PSS) 25.3 Comparative Example 2 (NiO) 40.1 Example 1 (NiO:K) 46.7 Example 2 (NiO:Na) 45.9

9 and 10 show conceptual diagrams for explaining why an organic solar cell using a hole transport layer according to an embodiment of the present invention exhibits excellent characteristics.

11 shows the energy levels of NiO, NiO:K, and NiO:Na shown in Table 2. It can be seen that the Fermi energy levels of NiO:K and NiO:Na have lower values than those of NiO, and the energy difference between the Fermi energy level and the valence band level also decreases. It is believed that this difference is caused by dipoles composed of ionic or covalent bonds present on the surface of nickel oxide. Among the dipoles, materials with a negative charge are materials with a charge of -1 composed of RSO ₃ ^- , and materials with a positive charge are materials with a charge of +1 Li, Na, K, Rb, Cs, alkali metals such as Fr.

10(a) shows the energy level at the interface between a NiO hole transport layer and a non-fullerene based BHJ (bulkheterojunction) photoactive layer, and FIG. 10(b) shows a NiO:K or NiO:Na hole transport layer and a non-fullerene based BHJ photoactive layer. BHJ (bulkheterojunction) is an expression of the energy level at the interface of the photoactive layer. Referring to FIGS. 10(a) and 10(b), due to dipoles formed on the surface of nickel oxide, the difference in Fermi energy level between the hole transport layer and the BHJ photoactive layer (indicated by a dotted line) is similar to that of normal without dipoles. It can be confirmed that it is reduced compared to nickel oxide. This decrease in Fermi energy level makes it easier for holes formed in the photoactive layer to be transferred to the hole transport layer. This change in the Fermi energy level increases the open-circuit voltage (Voc) of the organic solar cell and also causes an increase in efficiency.

As another embodiment of the organic solar cell according to the technical concept of the present invention, the hole transport layer may be made of a bi-layer of a separate nickel oxide layer (NiO) and a sulfonic acid salt layer. In the case of this embodiment, except for the manufacturing method of the hole transport layer, the rest was manufactured in the same manner as in Example 1 described above. The manufacturing method of the hole transport layer is as follows.

After primary spin-coating with a nickel oxide precursor solution, heat treatment was performed at 300° C. for 30 minutes to form a nickel oxide layer (NiO) having a thickness of 15 nm. Next, a sulfonic acid potassium salt solution or a sulfonic acid sodium salt solution was spin-coated on the nickel oxide layer, followed by heat treatment at 80° C. for 10 minutes to form a sulfonic acid salt layer, thereby forming a hole transport layer having a two-layer structure. The two-layer structure in which a spin coating layer is formed with a potassium sulfonic acid salt solution on top of the nickel oxide layer is expressed as NiO / K, and the two-layer structure in which a spin coating layer is formed with a sodium sulfonate salt solution on top of the nickel oxide layer is expressed as NiO / Na do. Example 3 is an organic solar cell using NiO/K as a hole transport layer, and Example 4 is an organic solar cell using NiO/Na.

The current density-voltage characteristics (current density-Voltage (J-V)) of the organic solar cell according to the above Examples and Comparative Examples were measured and shown in FIG. 11, and the efficiency is shown in Table 4 below.

hole transport layer
open voltage
[V] short circuit current
[mA cm ^-2 ] Fill Factor maximum efficiency
[%] Comparative Example 1
(PEDOT:PSS) 0.85 22.53 0.72 13.73 Comparative Example 2
(NiO) 0.79 22.77 0.68 12.19 Example 3 (NiO/K) 0.85 22.84 0.73 14.20 Example 4 (NiO/Na) 0.85 22.28 0.74 14.07

Even in the case of Examples 3 and 4, it was confirmed that they exhibited higher open-circuit voltage and higher maximum efficiency values than Comparative Examples 1 and 2.

As described above, in using nickel oxide as a hole transport layer of an organic solar cell having a non-fullerene-based photoactive layer, the effect of improving efficiency by dipoles by doping a sulfonic acid salt or forming a separate sulfonic acid salt layer on top of the nickel oxide layer. can be obtained.

<Production of Perovskite Solar Cell>

The hole transport layer according to the technical idea of the present invention can also be applied to perovskite solar cells to induce an increase in efficiency. The following examples are applied to perovskite solar cells.

The perovskite solar cell device was fabricated in the structure of ITO/NiO/MAPbI ₃ /PCBM/ZnO/Al. A glass substrate patterned with indium tin oxide (ITO), a transparent electrode on one side, was washed with distilled water, acetone, and isopropanol, and UV-Ozone treatment was performed for 30 minutes. Next, a hole transport layer was formed by coating to a thickness of 15 nm by spin coating using the nickel oxide mixed precursor solution prepared by the above-described method and heat-treating at 300° C. for 30 minutes. Next, to form a perovskite photoactive layer, a MAPbI ₃ (Methylammonium Lead Iodide) precursor solution was spin-coated at 4000 rpm for 25 seconds and heat-treated at 65°C for 1 minute and 100°C for 2 minutes. Next, an electron transport layer was formed by spin-coating a solution in which PC ₆₁ BM was dissolved at 2000 rpm for 30 seconds. Next, ZnO was formed by spin-coating at 4000 rpm for 40 seconds thereon, and Al was deposited thereon to a thickness of 100 nm as an electrode to complete device fabrication. Here, the case where NiO:K was used as the hole transport layer is referred to as Example 5, and the case where NiO:Na was used is referred to as Example 6. Meanwhile, as a comparative example, except for the hole transport layer, all other perovskite solar cells were manufactured in the same manner. In Comparative Example 3, PEDOT:PSS was used as the hole transport layer, and in Comparative Example 4, the above-described nickel oxide precursor solution was used.

Current density-voltage characteristics (current density-Voltage (J-V)) of the perovskite solar cell according to the above Examples and Comparative Examples were measured and shown in FIG. 12, and the efficiency is shown in Table 5 below.

hole transport layer
open voltage
[V] short circuit current
[mA cm ^-2 ] Fill Factor maximum efficiency
[%] Comparative Example 3
(PEDOT:PSS) 0.96 15.92 0.81 12.39 Comparative Example 4
(NiO) 1.05 20.67 0.76 16.48 Example 5 (NiO:K) 1.07 20.70 0.77 17.15 Example 6 (NiO:Na) 1.08 20.64 0.77 17.14

Even in the case of the perovskite solar cell, as in the organic solar cell, it was confirmed that Examples 5 and 6 exhibited higher open-circuit voltage and maximum efficiency than Comparative Examples.

Meanwhile, in FIG. 13 and Table 6, in the perovskite solar cells of Examples 5 and 6, the current density-voltage characteristics (current density- Voltage (J-V)) and efficiency are shown. Example 7 is a perovskite solar cell using NiO/K as a hole transport layer, and Example 8 is a perovskite solar cell using NiO/Na. The manufacturing method of the hole transport layer having a two-layer structure was performed in the same manner as in the example of the organic solar cell.

hole transport layer
open voltage
[V] short circuit current
[mA cm ^-2 ] Fill Factor maximum efficiency
[%] Comparative Example 2
(NiO) 1.05 20.67 0.76 16.48 Example 7 (NiO/K) 1.06 20.84 0.78 17.25 Example 8 (NiO/Na) 1.09 20.52 0.76 17.07

Referring to FIG. 13 and Table 6, it can be seen that in this case, as well as in the organic solar cell, Examples 7 and 8 exhibit better characteristics than Comparative Example 2.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (21)

a first electrode and a second electrode disposed facing each other;
a photoactive layer positioned between the first and second electrodes; and
A hole transport layer disposed between the second electrode and the photoactive layer;
The photoactive layer includes an organic material or a perovskite material,
The hole transport layer is a single layer in which a metal oxide and a dipole material are mixed with each other,
The dipole material comprises a sulfonic acid salt,
The sulfonic acid salt includes a hydroquinone sulfonic acid salt represented by Formula 1 below,
A solar cell having a metal oxide hole transport layer.
<Formula 1>

(In the formula, M ⁺ represents a cation.) delete delete delete delete According to claim 1,
The M ⁺ is any one of lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion and francium ion, a solar cell having a metal oxide hole transport layer. According to claim 1,
The hole transport layer has a thickness of 1 to 50 nm, a solar cell having a metal oxide hole transport layer. According to claim 1,
The photoactive layer made of the organic material has a two-layer structure in which an electron donor and an electron acceptor form a pn junction, a solar cell having a metal oxide hole transport layer. According to claim 1,
The photoactive layer made of the organic material has a bulk heterojunction structure composed of an electron donor and an electron acceptor, a solar cell having a metal oxide hole transport layer. According to claim 1,
The organic material includes a fullerene-based organic material or a non-fullerene-based organic material, a solar cell having a metal oxide hole transport layer. According to claim 10,
The non-fullerene-based organic material includes at least one selected from the group consisting of IDT-Br, ITIC, and Y6, a solar cell having a metal oxide hole transport layer. A solar cell manufacturing method comprising forming a first electrode, a hole transport layer, a photoactive layer, an electron transport layer, and a second electrode on one surface of a substrate,
The photoactive layer includes an organic material or a perovskite material,
Forming a hole transport layer, which is a single layer in which a metal oxide and a dipole material are mixed with each other, on top of the first electrode,
The dipole material comprises a sulfonic acid salt,
The sulfonic acid salt includes a hydroquinone sulfonic acid salt represented by Formula 1 below,
Method for manufacturing a solar cell having a metal oxide hole transport layer.
<Formula 1>

(In the formula, M ⁺ represents a cation.) delete delete delete delete According to claim 12,
The method of manufacturing a solar cell having a metal oxide hole transport layer, characterized in that the M ⁺ is any one of lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions and francium ions. According to claim 12,
The method of forming the hole transport layer,
Performed by a wet coating method using a metal oxide precursor solution in which a metal oxide precursor solution and a sulfonic acid salt solution are mixed,
Method for manufacturing a solar cell having a metal oxide hole transport layer. delete According to claim 18,
The metal oxide precursor solution is prepared by dissolving at least one selected from the group consisting of nickel acetate tetrahydrate, nickel acetylacetonate, nickel nitrate hexahydrate, nickel formate dihydrate, nickel chloride hydrate, and nickel ethylhexanoate. Method for manufacturing a battery. According to claim 18,
The method of manufacturing a solar cell having a metal oxide hole transport layer, wherein the sulfonic acid salt solution is obtained by dissolving a hydroquinone sulfonic acid salt represented by Formula 1 below.
<Formula 1>

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