KR20200001815A - Organic solar cell containing ternary based active layer and method of manufacturing the same - Google Patents

Abstract

The present invention relates to an organic solar cell including a ternary-based photoactive layer and a manufacturing method thereof. More specifically, the present invention relates to an organic solar cell which enables complementary light absorption of a donor component and an acceptor component, and obtains improved charge generation and extraction efficiency due to crystallinity control and molecular ordering of a photoactive layer. The present invention comprises: a first acceptor component; a non-crystalline donor component; and a second acceptor component.

Description

Organic solar cell comprising a three-component based photoactive layer and a method of manufacturing the same {Organic solar cell containing ternary based active layer and method of manufacturing the same}

The present invention relates to an organic solar cell, and more particularly, complementary light absorption of the donor component and the acceptor component, and the charge generation and extraction efficiency by crystallization control and molecular ordering of the photoactive layer The present invention relates to an organic solar cell including the improved three-component based photoactive layer and a manufacturing method thereof.

Recently, the depletion of fossil energy resources such as petroleum and coal has been intensified by the increase of global energy consumption and the rapid increase of transportation such as automobiles due to the industrialization. It is becoming. Accordingly, there is a growing interest in developing clean energy that can replace existing fossil energy sources, and further, research on technologies capable of producing clean energy at low cost is increasing. Currently, global electricity consumption is about 13 Terawatts (TW), which is expected to increase to more than 30 TW by 2050.

As a representative example of such alternative energy, a solar cell is in the spotlight, and a solar cell is a kind of device for directly converting solar energy into electrical energy. The global solar cell market shows a steep rise of about 35 to 40% annually. Currently, the main solar cell market is solar cells using crystalline silicon substrates. Briefly, its operation principle is that as light enters the solar cell from outside, valence band electrons of the p-type semiconductor are excited to the conduction band by the incident light energy. The electrons generate a pair of electron-holes inside the p-type semiconductor.

The electrons in these electron-hole pairs are transferred to the n-type semiconductor by an electric field existing between p-n junctions to supply current to the outside. At this time, when the p-type semiconductor and the n-type semiconductor are bonded to each other to form a junction, excess electrons present in the n-type semiconductor diffuse into the p-type semiconductor, while excess holes present in the p-type semiconductor are n It diffuses into the -type semiconductor, and the vacancies of the diffused electron-holes have a cation and an anion, respectively. At this time, the voltage is generated from the positive ion to the negative ion similar to the battery near the junction. However, in the case of the crystalline silicon solar cell described above, there is a limit in securing economic efficiency because the substrate material cost is high in the proportion of the total price and it must go through intermittent and complicated processes such as an ingot-wafer-cell-module.

As an alternative, research on organic solar cells is also actively underway. Organic solar cells use organic semiconductor materials that can realize conducting polymers or semiconductor devices that are both organic and well electricity, so they can be installed in windows, walls, and balconies of buildings to create a beautiful appearance and produce electricity at the same time. It is expected to be available. In particular, organic solar cells can be made into thin films with a thickness of several hundred nm and can be applied to a flexible structure. Therefore, they are expected to be applied to various applications such as presenting potential as energy sources of future mobile information systems.

Examples of the organic semiconductor used as the active layer of the organic solar cell include organic monomolecules and polymers. In the case of organic monomolecules, a method of forming a donor layer and an acceptor layer by heating in a vacuum is used. In the case of a thin film, a solution in which donor and acceptor materials are dissolved together is formed by spin coating, ink jet, or screen printing.

When the organic solar cell is irradiated with light, the donor material absorbs light to form an electron-hole pair (exciton), which is an energy mass in an excited state. Separated by holes. That is, the acceptor component having a high electron affinity rapidly attracts electrons to induce charge separation, and the holes remaining in the donor component layer are caused by the difference in concentration between the internal electric field and the accumulated charge formed by the work function difference of both electrodes. While moving to the anode, electrons are collected by moving to the cathode along the interior of the acceptor layer. The charge thus collected finally flows in the form of a current through an external circuit.

At this time, the active layer has a two-layer structure or a composite blend structure of the donor component and the acceptor component, optionally as a buffer layer through the hole transport layer between the anode and the active layer, and the electron transport layer between the cathode and the active layer. In particular, the blend structure is referred to as a bulk-heterojunction (BHJ) structure, which is a mixture of donor material and acceptor material within about 10 nm of the donor material and the donor and air structure compared to the bi-layer structure. It is known to provide an effect of increasing the area of the interceptor interface by several hundred times or more, thus increasing the possibility of charge separation and increasing the light absorption efficiency due to fine light scattering.

In this regard, in the case of a semiconductor polymer as a donor material constituting the active layer, a poly (p-phenylene vinylene) (PPV) -based component and a derivative of polythiophene (PT) have been studied. PF) -based components and copolymers thereof are also used as low band gap donor components. These donor components should primarily have a light absorption wavelength range that conforms to the solar spectrum, exhibit high light absorption, and excellent electrical properties such as charge mobility.

On the other hand, fullerene or derivatives thereof (PCBM) and the like are used as acceptor materials. In particular, fullerene derivatives are widely used as BHJ structural materials in combination with semiconductor polymers. As one of methods for increasing the efficiency of an organic solar cell using the BHJ structure, a tandem structure in which two or more active layers are laminated in the past has been developed. The active layer of such a tandem structure is reported to be able to improve the energy conversion efficiency because the absorption region is different and complementary solar absorption is possible. However, when two or more active layers are sequentially stacked in order to fabricate a tandem structure, not only there is a risk of damaging the lower active layer, but also a manufacturing process for mitigating them is inevitably complicated, so there is still a problem in commercialization.

Unlike the tandem method described above, recent research has improved the performance of solar cells by using a three-component mixture prepared by incorporating a donor component or an acceptor component in addition to a basic two-component mixture composed of a donor component and an acceptor component. However, the donor and / or acceptor components are agglomerated with each other to reduce the area of the donor-acceptor interface, thereby degrading the performance of the solar cell.

Republic of Korea Patent Publication No. 10-2006-0049942

The present invention has been made in view of the above, and it is possible to complementary light absorption of the donor component and the acceptor component, and charge generation and extraction efficiency by crystallization control and molecular ordering of the photoactive layer. An object of the present invention is to provide an organic solar cell including the improved three-component based photoactive layer and a method of manufacturing the same.

In order to solve the above problems, the present invention provides an amorphous donor component that forms an amorphous two-component mixture upon mixing with a crystalline first acceptor component, the first acceptor component, and when mixed with the amorphous two-component mixture. Provided is an organic solar cell including a photoactive layer including an amorphous second acceptor component to form a three-component mixture having a lower crystallinity than the first acceptor component.

According to an embodiment of the present invention, the donor component may be represented by the following Chemical Formula 1.

<Formula 1>

,

및

중에서 선택된 어느 하나, R₂는

이고, R₁`은 탄소수 4~20의 직쇄 또는 측쇄 알킬기, R<sub>2</sub>`은 탄소수 4~20의 직쇄 또는 측쇄 알킬기, R₂``은 탄소수 4~20의 직쇄 또는 측쇄 알킬기이다.In Formula 1, R ₁ is

,

And

Any one selected from R ₂

R ₁ ′ is a straight or branched chain alkyl group having 4 to 20 carbon atoms, R ₂ ′ is a straight or branched chain alkyl group having 4 to 20 carbon atoms, and R ₂ `` is a straight or branched chain alkyl group having 4 to 20 carbon atoms.

이고, R₂는

일 수 있다.In addition, according to an embodiment of the present invention, in Formula 1 R ₁ is

R ₂ is

Can be.

및

중에서 선택된 적어도 어느 하나고, R₃은 탄소수 4~8의 측쇄 또는 직쇄 알킬기일 수 있다.In addition, according to an embodiment of the present invention, the first acceptor component is

And

At least one selected from among, R ₃ may be a branched or straight chain alkyl group having 4 to 8 carbon atoms.

According to an embodiment of the present invention, the second acceptor component may be a fullerene derivative having 60 to 90 carbon atoms.

In addition, according to an embodiment of the present invention, the sum of the weight of the first acceptor component and the second acceptor component may be included in an amount of 100 to 300 parts by weight based on 100 parts by weight of the donor component.

In addition, according to an embodiment of the present invention, the first acceptor component and the second acceptor component may be included in a weight ratio of 1: 0.1 to 1:10.

In addition, according to an embodiment of the present invention, the three-component mixture in the Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum using X-ray wavelength may satisfy Condition 1 below. have.

<Condition 1>

In the above Condition 1, I _A1 is the highest peak intensity among the peaks of the first acceptor component, and I ₃ is the peak intensity of the three-component mixture in the scattering vector component (q _z ) where the I _A1 peak is located.

In another aspect, the present invention comprises the steps of mixing a crystalline first acceptor component, an amorphous donor component and an amorphous second acceptor component with a solvent to form a three-component mixture having a lower crystallinity than the first acceptor component And treating the three-component solution to form a photoactive layer.

According to one embodiment of the present invention, the solvent may include at least one selected from chloroform, chlorobenzene, dichlorobenzene, xylene, toluene, dichloromethane.

The organic solar cell according to the present invention is capable of complementary light absorption of the donor component and the acceptor component, the charge generation and extraction efficiency can be improved by the crystallization control and molecular ordering of the photoactive layer, Through this, an organic solar cell having excellent photoelectric conversion efficiency can be realized.

1 is a schematic cross-sectional view of an organic solar cell according to an embodiment of the present invention.
Figure 2a is a graph showing the light absorption spectrum using the UV-vis spectrophotometer of PBDTTPD-HT, ITIC, PC ₆₀ BM and PC ₇₀ BM.
Figure 2b is a graph showing the light absorption spectrum using the UV-vis spectrophotometer of PBDTTPD-HT, IDIC and PC ₇₀ BM.
Figure 3a is a graph showing the light absorption spectrum of the photoactive layer prepared in Comparative Example 1, Comparative Example 2 and Examples 1 to 4 measured by a UV-vis spectrophotometer.
Figure 3b is a graph showing the external quantum efficiency measurement results of the photoactive layer prepared in Comparative Example 1, Comparative Example 2 and Examples 1 to 4.
3C is a graph illustrating external quantum efficiency measurement results of the photoactive layers prepared in Comparative Example 2, Comparative Example 3 and Examples 5 to 7. FIG.
Figure 4a is a graph showing the photoluminescence emission spectrum analysis results of the photoactive layer prepared in Comparative Example 1, Comparative Example 2 and Examples 1 to 4.
Figure 4b is a graph showing the photoluminescence emission spectrum analysis results according to the weight ratio of ITIC and PC ₇₀ BM.
5A is an AFM image of the surface of the photoactive layer prepared in Comparative Example 1. FIG.
5B is an AFM image of the surface of the photoactive layer prepared in Example 1. FIG.
5C is an AFM image of the surface of the photoactive layer prepared in Example 2. FIG.
5D is an AFM image of the surface of the photoactive layer prepared in Comparative Example 2. FIG.
5E is a TEM image of the surface of the photoactive layer prepared in Comparative Example 1. FIG.
5F is a TEM image of the surface of the photoactive layer prepared in Example 1. FIG.
5G is a TEM image of the surface of the photoactive layer prepared in Example 2. FIG.
Figure 5h is a TEM image of the surface of the photoactive layer prepared in Comparative Example 2.
6A is an image showing grazing incidence wide-angle X-ray scattering pattern of PBDTTPD-HT.
6B is an image showing grazing incidence wide angle X-ray scattering pattern of ITIC.
6C is an image showing grazing-angle incident wide-angle X-ray scattering patterns of the photoactive layer prepared in Comparative Example 1. FIG.
FIG. 6D is an image showing grazing-angle incident wide-angle X-ray scattering patterns of the photoactive layer prepared in Example 2. FIG.
FIG. 6E is an image showing grazing-angle incident wide-angle X-ray scattering patterns of the photoactive layer prepared in Comparative Example 2. FIG.
FIG. 7 is an image showing grazing-angle incident wide-angle X-ray scattering spectra of the PBDTTPD-HT, ITIC, Comparative Example 1, Comparative Example 2, and the photoactive layer prepared in Example 2. FIG.
8 is a graph showing JV characteristics of the solar cells according to Comparative Example 1, Comparative Example 2 and Examples 1 to 4.

Although fullerene derivatives are used as an acceptor component included in the photoactive layer of the organic solar cell, there is a problem that the photoelectric conversion efficiency is low due to the narrow light absorption region. In order to solve this problem, a method of widening the light absorption region band by complementing the light absorption region band of the acceptor component and the donor component is used. However, the photoactive layer structure has a complex disadvantage.

In order to solve this problem, a three-component based photoactive layer consisting of two donor components and one acceptor component or one donor component and two acceptor components has been studied, but an acceptor component included in a conventional three-component based photoactive layer Silver has high crystallinity and agglomeration with each other, which adversely affects the nanomorphology of the photoactive layer or acts as a charge recombination center, resulting in a decrease in charge transport.

In order to solve the above problems, the present invention prevents or minimizes the problem that the acceptor components are agglomerated with each other by controlling the crystallinity and molecular ordering of the photoactive layer and optimizes the nanomorphology to generate and extract the charge of the photoactive layer. An organic solar cell with improved efficiency is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The organic solar cell according to the present invention includes a crystalline first acceptor component, an amorphous donor component that forms an amorphous two-component mixture when mixed with the first acceptor component, and the first two-component mixture when mixed with the amorphous two-component mixture. It includes a photoactive layer comprising a second acceptor component for forming a three-component mixture having a crystallinity lower than 100 million acceptor component, it may further comprise a transparent electrode, an electron transport layer and a counter electrode.

1 is a schematic cross-sectional view of an organic solar cell according to an embodiment of the present invention. Referring to this, the organic solar cell 10 according to the embodiment of the present invention has a transparent electrode 11 and an upper surface of the transparent electrode 11. It may include an electron transport layer 12 provided in, the photoactive layer 13 provided on the electron transport layer 12 and the counter electrode 14 provided on the photoactive layer.

The transparent electrode 11 includes indium-tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), indium gallium zinc oxide (IGZO), glass, polyethylene terephthalate (PET), and polyethylene (PEN) naphthalate, and polyimide, and may be preferably ITO.

The thickness of the transparent electrode 11 may be 100 to 300 nm, but is not limited thereto.

Next, the electron transport layer 12 may be provided on the transparent electrode 11.

The electron transport layer 12 may include any one selected from ZnO, TiO ₂ , SnO _2, and ITO, and may preferably include ZnO. The electron transport layer 12 may be formed on the transparent electrode by using a known method commonly used in the art, for example, may be a sol-gel method, but is not limited thereto.

The thickness of the electron transport layer 12 may be 20 to 100 nm, but is not limited thereto.

Next, a photoactive layer 13 is provided on the electron transport layer 12.

The photoactive layer 13 may include a crystalline first acceptor component, an amorphous donor component that forms an amorphous two-component mixture when mixed with the first acceptor component, and the first two-component mixture when mixed with the amorphous two-component mixture. And an amorphous second acceptor component that forms a three-component mixture having a lower crystallinity than the acceptor component.

Referring to FIG. 6C, when the amorphous donor component and the crystalline first acceptor component are mixed, the lamellar molecular arrangement present in the first acceptor component disappears. Referring to FIG. 6D, the donor component And in the case of the three-component mixture in which the second acceptor component is added to the two-component mixture in which the first acceptor component is mixed, it can be seen that the molecular arrangement in the lamellar form by the first acceptor component reappears. In addition, referring to Figure 7, it can be seen that the crystallinity of the three-component mixture is lower than the crystallinity of the first acceptor component.

As described above, through the crystallinity control and molecular ordering of the photoactive layer included in the solar cell according to the present invention, it is possible to prevent or minimize the problem that the acceptor components are aggregated with each other and to optimize the nanomorphology of the photoactive layer to provide photoactivity. It is possible to improve the charge generation and extraction efficiency of the layer.

In addition, the donor component, the first acceptor component and the second acceptor component may be complementary light absorption can be excellent in the light absorption characteristics of the photoactive layer. Referring to FIG. 2A, the donor component, the first acceptor component, and the second acceptor component included in the photoactive layer of the solar cell according to the exemplary embodiment of the present invention have different absorption wavelength bands, thereby enabling complementary light absorption. You can check it.

The sum of the weights of the first acceptor component and the second acceptor component may be included in an amount of 100 to 300 parts by weight, more preferably 100 to 200 parts by weight, based on 100 parts by weight of the donor component.

If the sum of the weights of the first acceptor component and the second acceptor component is less than 100 parts by weight or more than 300 parts by weight with respect to 100 parts by weight of the donor component, the short-circuit current and the effector of the device are greatly reduced and the solar cell The photoelectric conversion efficiency of can be reduced.

In addition, when the sum of the weights of the first acceptor component and the second acceptor component is included in an amount of 100 to 200 parts by weight based on 100 parts by weight of the donor component, the photoelectric conversion efficiency of the solar cell may be more excellent.

In addition, the first acceptor component and the second acceptor component may be included in the photoactive layer in a weight ratio of 1: 0.1 to 1:10.

If the weight ratio of the first acceptor component and the second acceptor component is less than 1: 0.1, the effect of increasing the crystallinity of the three-component mixture by the second acceptor component is increased when the two-component mixture and the second acceptor component are mixed. The photoelectric conversion efficiency of the solar cell may be reduced because it is not expressed at a desired level, and when it exceeds 1:10, the crystallinity of the first acceptor component is significantly lowered, resulting in the amorphous mixture of the three-component mixture. As a result, the photoelectric conversion efficiency of the solar cell may be reduced.

More preferably, the first acceptor component and the second acceptor component may be included in the photoactive layer in a weight ratio of 1: 0.2 to 1: 3, most preferably 1: 0.5 to 1: 2, and the weight ratio If the range is satisfied, the crystallinity of the three-component mixture is lower than that of the first acceptor component, and the effect of improving charge generation and extraction efficiency due to crystallinity control and molecular ordering of the photoactive layer is more excellent. The conversion efficiency can be further improved.

Referring to FIG. 3A, as the weight ratio of the second acceptor component is increased, the light absorption characteristic of the 650 to 800 nm wavelength band decreases, while as shown in FIG. 3B, the external ratio is increased as the weight ratio of the second acceptor component is increased. It can be seen that the quantum efficiency increases, and when the weight ratio of the second acceptor component exceeds a certain level, it can be seen that the external quantum efficiency is lowered.

Meanwhile, the donor component included in the photoactive layer of the solar cell according to the present invention may be represented by the following Chemical Formula 1.

<Formula 1>

,

및

중에서 선택된 어느 하나, R₂는

이고, R₁`은 탄소수 4~20의 직쇄 또는 측쇄 알킬기, R<sub>2</sub>`은 탄소수 4~20의 직쇄 또는 측쇄 알킬기, R₂``은 탄소수 4~20의 직쇄 또는 측쇄 알킬기일 수 있다.In Formula 1, R ₁ is

,

And

Any one selected from R ₂

R ₁ ′ may be a straight or branched alkyl group having 4 to 20 carbon atoms, R ₂ ′ may be a straight or branched alkyl group having 4 to 20 carbon atoms, and R ₂ `` may be a straight or branched alkyl group having 4 to 20 carbon atoms.

이고, R₂는

일 수 있으며, 이 경우 광활성층의 결정성 조절 및 분자 배열(molecular ordering)에 의한 전하 생성 및 추출 효율 향상 효과가 더욱 우수하여 태양전지의 광전변환효율을 더욱 향상될 수 있다.More preferably, in Formula 1, R ₁ is

R ₂ is

In this case, the effect of improving charge generation and extraction efficiency by crystallization and molecular ordering of the photoactive layer may be further improved, thereby further improving the photoelectric conversion efficiency of the solar cell.

및

중에서 선택된 적어도 어느 하나고, R₃은 탄소수 4~8의 측쇄 또는 직쇄 알킬기일 수 있다.In addition, the first acceptor component is

And

At least one selected from among, R ₃ may be a branched or straight chain alkyl group having 4 to 8 carbon atoms.

또는

, 가장 바람직하게는

일 수 있으며, 이 경우 광활성층의 결정성 조절 및 분자 배열(molecular ordering)에 의한 전하 생성 및 추출 효율 향상 효과가 더욱 우수하여 태양전지의 광전변환효율을 더욱 향상될 수 있다.More preferably the first acceptor component is

or

, Most preferably

In this case, the effect of improving charge generation and extraction efficiency by crystallization and molecular ordering of the photoactive layer may be further improved, thereby further improving the photoelectric conversion efficiency of the solar cell.

In addition, the second acceptor component may be a fullerene derivative having 60 to 90 carbon atoms, and may be, for example, PC ₆₀ BM or PC ₇₀ BM.

The photoactive layer may be formed by mixing a donor component, a first acceptor component, and a second acceptor component with a solvent and then treating the electron transport layer, and a method of treating the photoactive layer is a solution process known in the art. It may be formed using, for example, spin coating may be used, but is not limited thereto.

The solvent may be used without limitation as long as it is a solvent capable of dissolving the donor, first acceptor component and second acceptor component, and preferably chloroform, chlorobenzene, dichlorobenzene, xylene, toluene and dichloromethane. It may include any one selected from.

The thickness of the photoactive layer may be 60 to 300 nm, and if the thickness of the photoactive layer is less than 60 nm or more than 300 nm, there is a concern that the photoelectric conversion efficiency of the solar cell is lowered.

Next, a counter electrode 14 is provided on the photoactive layer 13. The counter electrode 15 includes silver, gold, aluminum, molybdenum oxide, copper, indium-tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), and indium gallium zinc oxide (IGZO). It may include at least one selected from, and preferably may be silver laminated on the molybdenum oxide.

The method of forming the counter electrode 14 may use a known method commonly used in the art for forming an electrode, and may be, for example, a thermal deposition method, but is not limited thereto.

The counter electrode 14 may have a thickness of 55 to 170 nm, preferably, when the counter electrode is silver laminated on molybdenum oxide, the thickness of the molybdenum oxide may be 5 to 20 nm, and the thickness of the silver may be 50 to 150 nm.

In the organic solar cell according to the present invention, the three-component mixture in Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum using X-ray wavelength may satisfy Condition 1 below. Accordingly, the crystallinity control and molecular ordering of the photoactive layer prevent or minimize the problem of aggregation of acceptor components and optimize the nanomorphology of the photoactive layer to improve the charge generation and extraction efficiency of the photoactive layer. Can be improved.

<Condition 1>

In Conditional Formula 1, I _A1 is the highest peak intensity among the peaks of the first acceptor component, that is, I _A1 is a grazing angle incident wide angle using an X-ray wavelength analyzed for a sample composed of the first acceptor component. The highest peak intensity among the peaks shown in the X-ray scattering spectrum, and I ₃ is the peak intensity of the three-component compound in the scattering vector component (q _z ) where the I _A1 peak is located.

Gradient-angle incident wide-angle X-ray scattering spectrum using the X-ray wavelength has a beam energy of 5-20 keV, an incident angle of 0.1-0.5 °, and a sample-to-detector distance of 100-500 mm. Can be measured under.

In the above Conditional Formula 1, when I ₃ / I _A1 is less than 0.2, the photoactive layer may have an amorphous molecular arrangement, and thus, the hole and electron transfer characteristics of the vertical direction may be degraded, thereby decreasing the photoelectric conversion efficiency of the solar cell. If it exceeds 0.8, phase separation between the donor component and the acceptor component may be developed to lower the charge generation and extraction efficiency of the photoactive layer, thereby lowering the photoelectric conversion efficiency of the solar cell.

Next, the manufacturing method of the organic solar cell which concerns on this invention is demonstrated.

The organic solar cell manufacturing method according to the present invention comprises the steps of preparing a two-component solution comprising an amorphous two-component mixture by mixing a crystalline first acceptor component and an amorphous donor component, Adding a 200 million acceptor component to prepare a three-component solution comprising a three-component mixture having a lower crystallinity than the first acceptor component and treating the three-component solution to form a photoactive layer.

The donor component, the first acceptor component, the second acceptor component, the solvent contained in the two-component solution, the method for treating the three-component solution, and a transparent electrode other than the photoactive layer included in the solar cell, the electron transport layer and the counterpart Since the configuration of the electrode is the same as described above in the organic solar cell according to the present invention, a detailed description thereof will be omitted.

Preparation Example 1 PBDTTPD-HT Preparation

(PBDTTPD-HT)를 합성하였다.With reference to a known paper (ACS Appl. Mater.Interfaces, 2017, 9 (38), pp 32939-32945)

(PBDTTPD-HT) was synthesized.

Preparation 2 ITIC Preparation

(ITIC)를 합성하였다.With reference to known papers (Adv. Mater. 2018, 27, 1170)

(ITIC) was synthesized.

Preparation 3 IDIC Preparation

(IDIC)를 합성하였다.With reference to a known paper (J. Am. Chem. Soc. 2016, 138, 2973-2976)

(IDIC) was synthesized.

Preparation Example 4 PC ₇₀ BM Ready

A commercial product PC ₇₀ BM (EM Index) was prepared.

Example 1

The glass substrate coated with indium tin oxide (ITO) was sonicated with acetone and isopropyl alcohol for 20 minutes and then dried in a vacuum oven at 120 ° C. The ZnO sol-gel precursor was spin-coated at 4000 rpm for 15 seconds on a dried substrate and then heat-treated at 200 ° C. for 10 minutes to form a ZnO electron transport layer (thickness: 20 nm).

Next, a photoactive layer was formed on the ZnO electron transport layer in a nitrogen atmosphere.

The donor component included in the photoactive layer was PBDTTPD-HT, the first acceptor component was ITIC, and the second acceptor component was PC ₇₀ BM, and these were dissolved in chloroform at a concentration of 7.5 mg / ml and then added as an additive. Iooctane was added at 0.8 volume% to prepare a three-component solution. The sum of the weights of the first acceptor component and the second acceptor component is included in 150 parts by weight based on the weight of the donor component, and the first acceptor component and the second acceptor component have a weight ratio of 1: 0.25. Included.

The three-component solution prepared on the electron transport layer was spin coated to form a three-component based photoactive layer.

Next, a solar cell was fabricated by forming a counter electrode in which MoOx (8 nm) and Ag (150 nm) were stacked on the photoactive layer using a thermal deposition method under reduced pressure (<10 ⁻⁶ Torr).

(Examples 2-4)

A solar cell was prepared in the same manner as in Example 1, but including a photoactive layer including the weight ratio of the first acceptor component and the second acceptor component in the numerical values shown in Table 1 below.

Example 5

In the same manner as in Example 1, a solar cell was manufactured using IDIC instead of ITIC as the first acceptor component.

Example 6

A solar cell including the photoactive layer including the first acceptor component and the second acceptor component in a weight ratio of 1: 0.67 was prepared in the same manner as in Example 5.

Example 7

In the same manner as in Example 5, a solar cell including a photoactive layer including a first acceptor component and a second acceptor component in a weight ratio of 1: 0.43 was manufactured.

Example 8

In the same manner as in Example 5, a solar cell including a photoactive layer including a first acceptor component and a second acceptor component in a weight ratio of 1: 1.5 was prepared.

(Comparative Example 1)

A solar cell was fabricated in the same manner as in Example 1 but provided with a photoactive layer containing no second acceptor component.

(Comparative Example 2)

A solar cell was prepared in the same manner as in Example 1 but having a photoactive layer containing no first acceptor component.

(Comparative Example 3)

A solar cell was prepared in the same manner as in Example 5, but provided with a photoactive layer containing no second acceptor component.

 Experimental Example 1

UV-vis spectrophotometer was used to evaluate the light absorption characteristics of PBDTTPD-HT, ITIC, PC ₆₀ BM, PC ₇₀ BM, and each component was dissolved in film (in flim) and chloroform in solution (in soulution). And the results are shown in FIGS. 2A and 2B.

Referring to FIG. 2A, the PBDTTPD-HT, the ITIC, and the PC ₇₀ BM have different absorption wavelength bands, and thus, complementary light absorption can be confirmed.

In addition, referring to Figure 2b, PBDTTPD-HT, IDIC and PC ₇₀ BM can be confirmed that the absorption wavelength is different and complementary light absorption is possible.

In addition, the light absorption characteristics and the external quantum efficiency according to the weight ratio of the first acceptor component and the second acceptor component included in the photoactive layer were measured, and the results are shown in FIGS. 3A to 3C.

Referring to Figure 3a second acceptor component while the light absorption characteristic of 650 ~ 800nm wavelength decreases with increasing weight ratio of (PC ₇₀ BM), the second acceptor component as shown in Figure 3b (PC ₇₀ It can be seen that the external quantum efficiency increases as the weight ratio of BM) increases, and when the weight ratio of the second acceptor component (PC ₇₀ BM) exceeds a certain level, the external quantum efficiency decreases. Can be.

In addition, when the weight ratio of the first acceptor component (ITIC) and the second acceptor component (PC ₇₀ BM) is 1: 0.67 (Example 2), it can be seen that it has the highest external quantum efficiency. Through this, it can be seen that the external quantum efficiency can be remarkably different depending on the weight ratio of the first acceptor component (ITIC) and the second acceptor component (PC ₇₀ BM).

Referring to FIG. 3C, the photoactive layer including the donor component (PBDTTPD-HT), the first acceptor component (IDIC), and the second acceptor component (PC ₇₀ BM) may include the first acceptor component (IDIC) or the first agent. It can be seen that the external quantum efficiency is remarkably superior to the photoactive layer containing no 200 million acceptor component (PC ₇₀ BM).

Experimental Example 2

In order to evaluate the charge generation efficiency of the photoactive layers prepared in Examples and Comparative Examples, photoluminescence emission spectra were analyzed for each photoactive layer under an excitation wavelength of 560 nm, and the results are shown in FIG. 4A. Shown.

Referring to FIG. 4A, the photoactive layer (PBDTTPD-HT) including only the donor component emits light at 670 nm, whereas the three-component based photoactive layer (Examples 1 to 4) did not have an emission peak at 670 nm. The excited electrons are believed to dissociate in the three-component based photoactive layer.

In addition, the photoactive layer (ITIC) containing only the first acceptor component has an emission peak at 760 nm, whereas the three-component based photoactive layer (Examples 1 to 4) has a significantly reduced emission peak at 760 nm, which is an excited electron. They are believed to dissociate in the three-component based photoactive layer.

4B is a graph showing photoluminescence emission spectra analysis results according to a weight ratio of the first acceptor component (ITIC) and the second acceptor component (PC ₇₀ BM). Referring to FIG. 4B, as the weight ratio of the second acceptor component (PC ₇₀ BM) increases, the emission peak at the 760 nm wavelength decreases almost linearly, and thus the first acceptor component (ITIC) is reduced. ) And the second acceptor component (PC ₇₀ BM) are photoexcited independently of each other.

Experimental Example 3

An AFM image (2 μm × 2 μm) of the surface of the photoactive layers prepared in Examples and Comparative Examples from a nanoscope instrument (Brunker) was scanned, and the results are shown in FIGS. 5A to 5D.

5A, 5B, 5C and 5D are AFM images of the surface of the photoactive layer prepared in Comparative Example 1, Example 1, Example 2 and Comparative Example 2, respectively. 5A to 5D, it can be seen that the photoactive layer surfaces prepared in Comparative Examples 1, 1, 2 and 2 have surface roughness values of 0.171, 0.980, 1.30, and 1.75 nm, respectively. .

In addition, using a transmission electron microscope (JEM-2100F, JEOL LTD) was analyzed for the surface of the photoactive layer prepared in Examples and Comparative Examples, its TEM image is shown in Figures 5e to 5h.

5E, 5F, 5G and 5H are TEM images of the surface of the photoactive layer prepared in Comparative Example 1, Example 1, Example 2 and Comparative Example 2, respectively.

Experimental Example 4

Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectra of the photoactive layers prepared in Examples and Comparative Examples were measured with a beam energy of 11.055 keV, an incident angle of 0.12 °, and the distance between the sample and the detector. The sample-to-detector distance was analyzed using X-ray wavelength under the condition of 221 mm, and the results are shown in FIGS. 6A to 6E.

6A, 6B, 6C, 6D, and 6E are PBDTTPD-HT (D), ITIC (NFA), and the photoactive layer of Comparative Example 1 (D: NFA: F ₇₀ A (1: 1.5: 0)), respectively. Grazing angles for the photoactive layer (D: NFA: F ₇₀ A (1: 0.9: 0.6)) of Example 2 and the photoactive layer (D: NFA: F ₇₀ A (1: 0: 1.5)) of Comparative Example 2 It is an image showing the result of incident wide-angle X-ray scattering analysis.

Referring to FIG. 6A, the donor component (D) is out-of-plane (010) indicating that π-π stacking is oriented in face-on mode along the Qz axis at 1.622 Hz. ) Shows diffraction.

Referring to FIG. 6B, the molecular arrangement of the strong symmetric lamellar form of the first acceptor component (NFA) can be confirmed.

Referring to FIG. 6C, it can be seen that the lamellar molecular arrangement disappears when the donor component and the first acceptor component are mixed, which is considered to be due to excellent miscibility of the donor component and the first acceptor component.

Referring to FIG. 6E, it can be seen that an azimuthally isotropic ring pattern appears due to the aggregation of the second acceptor component when the donor component (D) and the second acceptor component (F ₇₀ A) are mixed. .

Referring to FIG. 6D, when the donor component, the first acceptor component, and the second acceptor component are included, the lamellar molecular arrangement by the first acceptor component (NFA) may be reappeared.

7 is PBDTTPD-HT, ITIC, photoactive layer of Comparative Example 1 (PBDTTPD-HT + ITIC), photoactive layer of Example 2 (PBDTTPD-HT + ITIC + PC ₇₀ BM), photoactive layer of Comparative Example 2 (PBDTTPD The line-cut intensity obtained along the out-of-plane direction in the 2D-GIWAXS pattern for -HT + PC ₇₀ BM). Referring to this, no peak was found in the donor component (PBDTTPD-HT) alone, and the first acceptor component (ITIC) had a peak corresponding to a molecular arrangement in the form of lamelae. When the donor component (PBDTTPD-HT) and the first acceptor component (ITIC) are mixed, it can be seen that all the peaks that existed in the first acceptor component disappeared, and the donor component (PBDTTPD-HT) and the first acceptor When both the component (ITIC) and the second acceptor component (PC ₇₀ BM) are included, the peak corresponding to the lamellar molecular arrangement by the first acceptor component (ITIC) may be reappeared.

In addition, the three-component mixture (PBDTTPD-HT + ITIC + PC ₇₀ BM) in the relatively highest peak intensity (I _A1 ) and the corresponding scattering vector component (q _z ) among the peaks of the first acceptor component (ITIC). I ₃ / I _A1 was 0.44 when the peak intensity (I ₃ ) of was substituted in Conditional Expression 1.

Experimental Example 5

After measuring the open voltage, the short-circuit current density and the fill factor from the J-V curve of the organic solar cells prepared in Examples and Comparative Examples, the photoelectric conversion efficiency (PCE) was calculated and shown in Table 1 below.

Specifically, the open-circuit voltage, short-circuit current density and fill factor values were measured for the JV characteristics using a Keithley 2401 source device under light intensity AM 1.5 G (100 mW / cm ² ) illumination (Newport). Shown. In addition, the photoelectric conversion efficiency was calculated from the measured JV characteristics.

division Photoactive layer Organic solar cell donor
ingredient Acceptor components PCE (%) matter Parts by weight 1st acceptor
ingredient 2nd acceptor
ingredient A1: A2 Parts by weight matter matter Comparative Example 1 PBDTTPD-HT 100 ITIC - 1: 0 150 9.95 Example 1 PBDTTPD-HT 100 ITIC PC ₇₀ BM 1: 0.25 150 11.89 Example 2 PBDTTPD-HT 100 ITIC PC ₇₀ BM 1: 0.67 150 12.09 Example 3 PBDTTPD-HT 100 ITIC PC ₇₀ BM 1: 1.5 150 11.79 Example 4 PBDTTPD-HT 100 ITIC PC ₇₀ BM 1: 4 150 10.07 Comparative Example 2 PBDTTPD-HT 100 - PC ₇₀ BM 0: 1 150 7.78 Comparative Example 3 PBDTTPD-HT 100 IDIC - 1: 0 150 10.46 Example 5 PBDTTPD-HT 100 IDIC PC ₇₀ BM 1: 0.25 150 11.02 Example 6 PBDTTPD-HT 100 IDIC PC ₇₀ BM 1: 0.67 150 11.29 * A1: A2 = weight ratio of the first acceptor component and the second acceptor component

Referring to Table 1, a photoactive layer in which a solar cell including a donor component, a first acceptor component, and a second acceptor component does not include a first acceptor component or a second acceptor component It can be seen that the photoelectric conversion efficiency (PCE) is significantly superior to the solar cell having a. In particular, it can be seen that the photoelectric conversion efficiency of the solar cell having the photoactive layer including the first acceptor component and the second acceptor component in a weight ratio of 1: 0.67 is the most excellent. In addition, when the weight ratios of the first acceptor component and the second acceptor component are the same, it can be seen that the solar cell using ITIC as the first acceptor component is more excellent in photoelectric conversion efficiency than the solar cell using IDIC.

Experimental Example 6

The hole mobility and the electron mobility of the organic solar cells prepared in Comparative Example 2, Comparative Example 3, Example 5, Example 6 and Example 8 were measured and the results are shown in Table 2 below.

Solar cell Mobility (10 ^-3 cm ^-2 V ^-1 S ^-1 ) μ _h / μ _e Hole mobility (μ _h ) Electron Mobility (μ _e ) Comparative Example 3 1.71 1.12 1.53 Example 5 2.34 1.62 1.44 Example 6 2.61 2.08 1.25 Example 8 2.1 1.02 2.06 Comparative Example 2 1.99 1.15 1.73

Referring to Table 2, a solar cell having a photoactive layer including a first acceptor component (IDIC) and a second acceptor component (PC ₇₀ BM) in a weight ratio of 1: 0.67 is a first acceptor component or It can be seen that the hole mobility and the electron mobility are remarkably superior to the solar cell having the photoactive layer containing no second acceptor component.

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments set forth herein, and those skilled in the art who understand the spirit of the present invention may add components within the scope of the same idea. Other embodiments may be easily proposed by changing, deleting, adding, and the like, but this will also fall within the spirit of the present invention.

10: organic solar cell
11: transparent substrate
12: electron transport layer
13: photoactive layer
14: counter electrode

Claims (10)

Crystalline first acceptor component;
An amorphous donor component that forms an amorphous two-component mixture when mixed with the first acceptor component; And
A second acceptor component which, when mixed with the amorphous two-component mixture, forms a three-component mixture having a lower crystallinity than the first acceptor component;
Organic solar cell comprising a photoactive layer comprising a.
The method of claim 1,
The donor component is an organic solar cell represented by the following formula (1).
<Formula 1>

In Formula 1, R ₁ is

,

And

Any one selected from
R ₂ is

ego,
R ₁ ′ is a straight or branched alkyl group having 4 to 20 carbon atoms, R ₂ ′ is a straight or branched alkyl group having 4 to 20 carbon atoms, and R ₂ `` is a straight or branched alkyl group having 4 to 20 carbon atoms.
The method of claim 2,
In Formula 1, R ₁ is

R ₂ is

Organic solar cell.
The method of claim 1,
The first acceptor component is

And

At least one selected from among, R ₃ is an organic solar cell having 4 to 8 carbon atoms in the branched or straight chain alkyl group.
The method of claim 1,
The second acceptor component is an organic solar cell having a C 60-90 fullerene derivative.
The method of claim 1,
The sum of the weights of the first acceptor component and the second acceptor component is 100 to 300 parts by weight based on 100 parts by weight of the donor component.
The method of claim 6,
The first acceptor component and the second acceptor component is an organic solar cell comprising a weight ratio of 1: 0.1 ~ 1:10.
The method of claim 1,
An organic solar cell satisfying the following Conditional Formula 1 in Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum using X-ray wavelength.
<Condition 1>

In the above Condition 1, I _A1 is the highest peak intensity among the peaks of the first acceptor component, and I ₃ is the peak intensity of the three-component mixture in the scattering vector component (q _z ) where the I _A1 peak is located.
Mixing a crystalline first acceptor component, an amorphous donor component, and an amorphous second acceptor component with a solvent to form a three-component mixture having a lower crystallinity than the first acceptor component; And
Treating the three-component solution to form a photoactive layer;
Method for producing an organic solar cell comprising a.
The method of claim 9,
The solvent is a method of manufacturing an organic solar cell comprising at least one selected from chloroform, chlorobenzene, dichlorobenzene, xylene, toluene and dichloromethane.

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