WO2014061857A1 - Effective p-type dopant and rhenium oxide for overcoming s-type current-voltage graph in organic photovoltaic cell using electron donor with low highest occupied molecular orbital energy level - Google Patents

Abstract

Provided are a first electrode, a first hole transport layer that is formed on the first electrode and has a p-type dopant contained in a first hole transport material, a second hole transport layer that is formed on the first hole transport layer, a photoactive layer that is formed on the second hole transport layer and has a donor layer and an acceptor layer, and an organic photovoltaic cell that has a second electrode which is formed on the photoactive layer, in which the highest occupied molecular orbital energy level of the donor layer is -5.6 eV or less, the highest occupied molecular orbital energy level of the second hole transport layer is higher than the highest occupied molecular orbital energy level of the donor layer by 0 or 0.1 eV, and a Fermi level of the p-type dopant is lower than a highest occupied molecular orbital energy level of the first hole transport material.

Description

Effective Oxide Dopant, Rhenium Oxide for Overcoming S-Type Current-Voltage Graphs in Organic Solar Cells Using Low Top-Level Molecular Orbital Energy Level Electron Donors

The present invention relates to an organic solar cell and a method of manufacturing the same, and more particularly, to an organic solar cell having excellent power conversion efficiency including a p-type doped hole transport layer.

Organic solar cells are attracting attention as sustainable energy sources because they can produce energy at a lower cost than inorganic semiconductors using silicon. Until recently, the power conversion efficiency (PCE) of organic solar cells has been reported to reach a maximum of about 8%, but the efficiency of conventional organic solar cells is much lower than that, which makes it difficult to use in actual solar power generation. have.

The power conversion efficiency (PCE) of an organic solar cell is calculated by the following equation:

PCE = (Voc × Jsc × FF) / Pin

Where Voc is the open voltage, Jsc is the short-circuit current density, FF is the fill factor, and Pin is the incident light intensity.

In order to increase power conversion efficiency of the organic solar cell, a method of increasing Voc may be used. Voc is determined by the difference between the highest level occupied molecular orbital energy level of the donor layer of the organic solar cell and the lowest occupied molecular orbital energy level of the acceptor layer, so that the highest occupied molecular orbital energy in the donor layer is increased to increase the Voc. A method using low level materials can be used. In this case, however, a large contact resistance occurs between the anode and the donor layer, resulting in an S-shape on the current-voltage graph, which reduces the filling rate of the organic solar cell, thereby reducing the power conversion efficiency. This happens.

As such, there are many difficulties in improving the power conversion efficiency of the organic solar cell to a satisfactory level and a method for improving the organic solar cell is required.

An organic solar cell with improved power conversion efficiency is provided. In particular, it is to provide an organic solar cell having improved filling rate and power conversion efficiency by reducing the S-shape on a voltage-current graph.

According to one aspect, the first electrode is formed on the first electrode, the first hole transport layer containing a p-type dopant in the first hole transport material second hole transport layer formed on the first hole transport layer the second hole transport layer And a second electrode formed on the photoactive layer, wherein the photoactive layer includes a photoactive layer including a donor layer and an acceptor layer, and the donor layer has a highest molecular weight orbital energy level of -5.6 eV or less; The highest level occupant molecular orbital energy level of the hole transport layer is 0 to 0.1 eV higher than the highest occupant molecular orbital energy level of the donor layer, and the Fermi level of the p-type dopant is the highest occupant molecular orbital energy of the first hole transport material. An organic solar cell lower than the level is provided.

The p-type dopant may include rhenium oxide.

The first hole transport material may include TAPC (1,1-bis [4- [N, N'-di (p-tolyl) amino] phenyl] cyclohexane).

The second hole transport layer may include the first hole transport material.

The second hole transport layer may include the first hole transport material, and the first hole transport material is TAPC (1,1-bis [4- [N, N'-di (p-tolyl) amino] phenyl ] Cyclohexane).

The p-type dopant may be 25 mol% based on the total weight of the first hole transport layer.

The donor layer is DCV5T (α, α-bis (2,2-dicyanovinyl) -quinquethiophene), SubPc (subphthalocyanine), DIP (diindenoperylene), DBP (tetraphenyl-dibenzoperiflanthene), merocyanine dye, squaraine Squaraine dye, DTDCTP (2-{[2- (5-N, N-di (p-tolyl) aminothiophen-2-yl) -pyrimidin-5-yl] methylene} -malononitrile), and DTS ( PTTh ₂ ) ₂ (5,5'-bis {(4- (7-hexylthiophen-2-yl) thiophene-2-yl)-[1,2,5] -thiadiazolo [3,4, -c] pyridine} -3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene).

The acceptor layer comprises C60, C70, [60] PCBM ([6 6] -phenyl-C61-butylic acid methyl ester), and [70] PCBM ([6,6] -phenyl-C71-butylic acid methyl Esters).

The donor layer and the second hole transport layer may be in contact with each other.

The first electrode may include ITO.

The organic solar cell may further include an exciton blocking layer interposed between the photoactive layer and the second electrode.

According to another aspect, forming a first electrode on a substrate to form a first hole transport layer using a first hole transport material and a p-type dopant on the first electrode, Fermi of the p-type dopant A level is lower than the highest level occupant molecular orbital energy level of the first hole transport material. A second hole transport layer is formed on the first hole transport layer. A donor layer and an acceptor layer are formed on the second hole transport layer. A step of forming a photoactive layer, wherein the highest level occupant molecular orbital energy level of the donor layer is less than -5.6 eV and the highest level occupant molecular orbital energy level of the second hole transport layer is the highest occupied molecular orbital energy level of the donor layer A method of manufacturing an organic solar cell is provided, comprising the step of forming a second electrode on the photoactive layer higher by 0 to 0.1 eV.

Rhenium oxide may be used as the p-type dopant.

TAPC may be used as the first hole transport material.

The second hole transport layer may be formed using the first hole transport material.

The p-type dopant may be 25 mol% based on the total weight of the first hole transport layer.

The donor layer may be formed using at least one of DCV5T, SubPc, DIP, DBP, merocyanine dye, squaraine dye, DTDCTP, and DTS (PTTh ₂ ) ₂ .

The organic solar cell according to an aspect of the present invention improves power conversion efficiency by preventing exciton quenching in the hole transport layer, reducing contact resistance between the electrode and the donor layer, and reducing the occurrence of the S-shape.

1 is a cross-sectional view schematically showing the structure of an organic solar cell according to one embodiment.

2 is a cross-sectional view schematically showing the structure of an organic solar cell according to another embodiment.

3 is a view schematically showing the highest level occupied molecular orbital and lowest level occupied molecular orbital energy levels of each layer constituting the organic solar cell according to one embodiment.

4 is a graph showing the voltage-current relationship of the organic solar cell according to Example 1 and Comparative Examples 1 and 2.

5 is a graph showing the voltage-current relationship of the organic solar cell according to Example 1 and Comparative Examples 3 to 6.

6 is a graph showing the voltage-current relationship of the organic solar cells according to Examples 1 to 5.

7 is a graph illustrating a voltage-current relationship of organic solar cells according to Comparative Examples 6 to 10. FIG.

Hereinafter, with reference to the embodiments of the present invention shown in the accompanying drawings will be described in detail the configuration and operation of the present invention.

1 is a cross-sectional view schematically showing the structure of an organic solar cell 100 according to an embodiment.

The organic solar cell 100 according to the embodiment includes a first hole 111 formed on the first electrode 111 and a second hole formed on the first hole transport layer 121. A transport layer 131 is formed on the second hole transport layer 131 and a photoactive layer 150 including a donor layer 151 and an acceptor layer 152 and a second electrode 171 formed on the photoactive layer 150. )

The photoactive layer 150 absorbs light to generate excitons and draws electrons from the excitons based on the principle of electron donation and reception to separate holes and electrons, thereby flowing a current through the organic solar cell 100. The photoactive layer 150 is composed of a donor layer 151 and an acceptor layer 152.

The donor layer 151 is formed of an organic material excellent in photoreaction. The donor layer 151 absorbs light to generate excitons in which electrons and holes are combined. Since the generated exciton has a very short diffusion distance of several tens to several tens of nanometers, the donor layer 151 is formed to absorb light sufficiently and to have a thick thickness to overcome the short diffusion distance of the exciton.

The acceptor layer 152 is formed of a material having high electron affinity. The acceptor layer 152 receives electrons from excitons at the interface between the donor layer 151 and the acceptor layer 152. The acceptor layer 152 is formed to smoothly receive electrons from the interface and to quickly transport the received electrons toward the second electrode 171.

The first hole transport layer 121 and the second hole transport layer 131 are formed of a hole transport material. The first hole transport layer 121 and the second hole transport layer 131 transport the holes formed by the exciton lost electrons at the interface between the donor layer 151 and the acceptor layer 152 toward the first electrode 111. Do it.

The first hole transport layer 121 is a layer in which the p-type dopant is included in the first hole transport material. For example, the first hole transport layer 121 is formed by doping the p-type dopant with impurities in the first hole transport material. The second hole transport layer 131 is formed of a second hole transport material.

The first electrode 111 is formed of a transparent electrode that can easily pass light to reach the donor layer 151. The first electrode 111 acts as an anode for receiving holes that have passed through the hole transport layers 121 and 131. Since the first electrode 111 contacts or approaches the first hole transport layer 121, contact resistance may occur at an interface thereof.

The second electrode 171 is formed of a metal electrode to receive electrons transported from the acceptor layer 152 to flow a current. The second electrode 171 acts as a cathode to emit electrons to an external conductive line. Since the second electrode 171 is in contact with or close to the acceptor layer 152 which is a part of the photoactive layer 150, a contact resistance may be greatly generated at a portion where the metal electrode and the organic material contact each other. For example, Al may be used as the second electrode 171.

The power conversion efficiency (PCE) of the organic solar cell 100 is proportional to the open voltage Voc, and the open voltage is the highest occupied molecular orbital energy level of the donor layer 151 and the lowest occupied ratio of the acceptor layer 152. Since the molecular orbital energy level is proportional to the difference, it is necessary to lower the highest molecular weight orbital energy level of the donor layer 151 to increase the power conversion efficiency. The highest level occupant molecular orbital energy level of the donor layer 151 of the organic solar cell 100 is -5.6 eV or less.

If the donor layer and the first electrode of the organic solar cell are in close contact with each other or are located in close proximity to each other, the highest level molecular molecular orbital energy level of the donor layer is lowered and the Fermi level of the first electrode is lower than that of the first electrode. When the difference is turned on, the contact resistance between the donor layer and the first electrode may increase. This increase in contact resistance may cause the S-shape to appear on the voltage-current graph, which is undesirable because it reduces the filling rate of the organic solar cell and finally reduces the power conversion efficiency.

In the organic solar cell 100, the donor layer 151 and the first electrode 111 are interposed between the donor layer 151 and the first electrode 111 with a first hole transport layer 121 and a second hole transport layer 131 interposed therebetween. ), The contact resistance between them becomes small. In particular, since the difference between the highest level occupant molecular orbital energy level of the second hole transport layer 131 and the highest level occupant molecular orbital energy level of the donor layer 151 is small, the S-shape does not appear on the voltage-current graph. The difference between the highest level occupied molecular orbital energy level of the second hole transport layer 131 of the organic solar cell 100 and the highest occupied molecular orbital energy level of the donor layer 151 is controlled to about 0.1 eV or less.

The first hole transport layer 121 of the organic solar cell 100 includes a p-type dopant in the first hole transport material to facilitate the transport of holes. Since the p-type dopant is lower than the highest level occupant molecular orbital energy level of the first hole transport material, the p-type dopant accepts electrons from the first hole transport material to generate holes, thereby improving hole transportability. The Fermi level of the p-type dopant included in the first hole transport layer 121 of the organic solar cell 100 is much lower than the highest molecular weight orbital energy level of the first hole transport material. This rarely appears.

The charge carrier density increases and the first hole increases because the difference between the Fermi level of the p-type dopant included in the first hole transport layer 121 of the organic solar cell 100 and the highest molecular weight orbital energy level of the first hole transport material is large. Since a lot of band bending occurs between the transport layer 121 and the first electrode 111, the contact resistance of the interface between the first hole transport layer 121 and the first electrode 111 is reduced. The decrease in contact resistance prevents the S-shape from appearing on the voltage-current graph.

The p-type dopant used as the impurity concept in the first hole transport layer 121 may be rhenium oxide. Various materials may be used as the p-type dopant, but the organic solar cell 100 according to the exemplary embodiment may include a p-type dopant having a low Fermi level as described above and may include, for example, rhenium oxide.

The first hole transport material used as the host concept of the first hole transport layer 121 may be TAPC (1,1-bis [4- [N, N'-di (p-tolyl) amino] phenyl] cyclohexane). have. Since the difference between the Fermi level of the p-type dopant and the energy level of the highest molecular occupancy of the TAPC is quite large, the expression of the S-shape on the voltage-current graph can be suppressed.

The second hole transport layer 131 may be formed of a second hole transport material, and the second hole transport material may be the same material as the first hole transport material. When the second hole transport layer 131 is formed using the first hole transport material, the hole transport layer may be simply formed in one process without being formed through two processes using two separate materials.

In the present specification, the first hole transport layer 121 and the second hole transport layer 131 are described as two separate layers, but the first hole transport layer 121 and the second hole transport layer 131 are not limited thereto. As a hole transport layer, a sub-layer having a part thickness close to the first electrode 211 of the one hole transport layer may be doped with a p-type dopant, and the remaining sub-layer may be an undoped layer.

When the second hole transport layer 131 is formed of the first hole transport material, the first hole transport material may be TAPC. In this case, since the difference between the Fermi level of the p-type dopant and the energy level of the highest molecular occupancy of the TAPC is large, the expression of the S-shape is suppressed and the first hole transport layer 121 and the second hole transport layer 131 are processed in one process. It can form within and a manufacturing process becomes simple.

The content of the p-type dopant may be 25 mol% relative to the total weight of the first hole transport layer 121. When the content of the p-type dopant satisfies the above range, the charge carrier density may increase to reach a more satisfactory level of filling rate and power conversion efficiency.

Donor layer 151 is DCV5T (α, α-bis (2,2-dicyanovinyl) -quinquethiophene), SubPc (subphthalocyanine), DIP (diindenoperylene), DBP (tetraphenyl-dibenzoperiflanthene), merocyanine dye, Squaraine dye, DTDCTP (2-{[2- (5-N, N-di (p-tolyl) aminothiophen-2-yl) -pyrimidin-5-yl] methylene} -malononitrile), and DTS (PTTh ₂ ) ₂ (5,5'-bis {(4- (7-hexylthiophen-2-yl) thiophene-2-yl)-[1,2,5] -thiadiazolo [3,4, -c] pyridine} -3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene). The donor layer 151 is formed of a material having a low energy level of -5.6 eV or less in order to increase the open voltage. For example, the donor layer 151 may include DCV5T.

The acceptor layer 152 is formed of a material having high electron affinity. Materials for forming the acceptor layer 152 include C60, C70, [60] PCBM ([6 6] -phenyl-C61-butylic acid methyl ester), and [70] PCBM ([6,6] -phenyl- C71-butylic acid methyl ester) can be mentioned. The acceptor layer 152 may be formed using, for example, C60.

The donor layer 151 and the second hole transport layer 121 may be in contact with each other.

The first electrode 111 may be formed to include indium tin oxide (ITO) having transparent, excellent conductivity, and high Fermi level, but is not limited thereto.

2 is a schematic cross-sectional view of a structure of an organic solar cell 200 according to another embodiment.

An organic solar cell 200 according to an embodiment includes a first electrode 211; A first hole transport layer 221 formed on the first electrode 211; A second hole transport layer 231 formed on the first hole transport layer 221; A photoactive layer 250 formed on the second hole transport layer 231 and including a donor layer 251 and an acceptor layer 252; And an exciton blocking layer 261 formed on the photoactive layer 250 and a second electrode 271 formed on the exciton blocking layer 261.

In order to increase the open voltage Voc of the organic solar cell 200, the donor layer 251 is formed of a material having a low highest molecular weight orbital energy level and has a highest molecular weight orbital energy level of -5.6 eV or less. It is formed of a substance.

The second hole transport layer 231 is formed of a material in which the highest level occupant molecular orbital energy level of the second hole transport layer 231 is smaller than the highest level occupant molecular orbital energy level of the donor layer 251. It is formed of a material that is 0.1 eV or less.

The first hole transport layer 221 is formed by doping the first hole transport material with a p-type dopant, and the Fermi level of the p-type dopant is lower than the highest occupying molecular orbital energy level of the first hole transport material. As a result, a lot of band bending occurs between the first hole transport layer 221 and the first electrode 211, thereby reducing the contact resistance at the interface between the first hole transport layer 221 and the first electrode 211.

The exciton blocking layer 261 may be formed of, for example, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), but is not limited thereto.

The organic solar cell 200 is suppressed the expression of the S-shape on the voltage-current graph to improve the filling rate and power conversion efficiency.

FIG. 3 schematically illustrates energy levels of the highest level occupied molecule and the lowest level occupied molecular orbital energy of each layer constituting the organic solar cell 200 according to an exemplary embodiment.

Referring to FIG. 3, at the interface between the donor layer 251 and the acceptor layer 252, a large energy gap is formed to apply a high open voltage. For example, the highest occupied molecular orbital energy level of the donor layer 251 is about -5.6 eV, and the lowest occupied molecular orbital energy level of the acceptor layer 252 is about -4.5 eV. The energy gap is about 1.1 eV.

The highest occupied molecular orbital energy level of the second hole transport layer 231 is similar to the highest occupied molecular orbital energy level of the donor layer 251, and a low energy gap is formed, for example, the highest occupant molecules of both layers. The difference in orbital energy level is low, below about 0.1 eV.

The Fermi level of the p-type dopant included as an impurity in the first hole transport layer 221 is much lower than the highest molecular weight orbital energy level of the first hole transport material. Since the Fermi level of the p-type dopant is -6.8 eV, the Fermi level of the p-type dopant is about 1.3 eV below the molecular orbital energy level of the first hole transport material.

The organic solar cell has the highest level occupant molecular orbital energy level of the first hole transport material constituting the first hole transport layer 221, the Fermi level of the p-type dopant, and the highest level occupant molecular track of the second hole transport layer 231. By controlling the energy level and the highest level occupant molecular orbital energy level of the donor layer 251, the exciton quenching phenomenon is prevented in the second hole transport layer 231 and the contact between the first electrode 211 and the first hole transport layer 221 is achieved. The resistance can be reduced and the occurrence of the S-shape can be reduced.

Hereinafter, a method of manufacturing an organic solar cell according to the present invention will be described with reference to FIG. 1. However, the present invention is not limited thereto.

In the manufacturing method of the organic solar cell 100 according to an embodiment, the step of forming the first electrode 111 on the substrate using a first hole transport material and the p-type dopant on the first electrode 111 Forming a first hole transport layer 121, forming a first hole transport layer 121 such that the Fermi level of the p-type dopant is lower than the highest molecular weight orbital energy level of the first hole transport material Forming a second hole transport layer 131 on the first hole transport layer 121 Photoactive layer 150 including a donor layer 151 and an acceptor layer 152 on the second hole transport layer 131 In this step, the highest molecular weight molecular orbital energy level of the donor layer 151 is -5.6 eV or less and the highest molecular weight molecular orbital energy level of the second hole transport layer 131 is equal to that of the donor layer 151. The photoactive layer 150 is shaped to be 0 to 0.1 eV larger than the highest occupied molecular orbital energy level. Forming a second electrode on the photoactive layer.

As the substrate (not shown), a substrate used for a conventional organic solar cell can be used, and a glass substrate or a transparent plastic substrate excellent in mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and waterproofness can be used. For example, the substrate can be formed of a transparent glass material mainly containing SiO 2.

The first electrode 111 is formed on the substrate. As the first electrode 111, ITO may be used as an anode and may be transparent, excellent in conductivity, and have a high Fermi level, but is not limited thereto.

The first hole transport layer 121 is formed on the first electrode 111. The first hole transport layer 121 may be formed by doping the p-type dopant to the first hole transport material. For the first hole transport material and the p-type dopant, the Fermi level of the p-type dopant is lower than the highest molecular weight orbital energy level of the first hole transport material. For example, TAPC may be used as the first hole transport material, and rhenium oxide may be used as the p-type dopant.

The p-type dopant may be used in an amount of 25 mol% based on the total weight of the first hole transport layer 131. When the content of the p-type dopant satisfies the above range, the charge carrier density may increase to reach a more satisfactory level of filling rate and power conversion efficiency.

The second hole transport layer 131 is formed on the first hole transport layer 121. The second hole transport layer 131 may be formed using a second hole transport material. As the second hole transport material, a material having a difference between the highest level occupant molecular orbital energy level of the second hole transport layer 131 and the highest level occupant molecular orbital energy level of the donor layer 151 is about 0.1 eV or less. As the second hole transport material, for example, the same material as the first hole transport material may be used.

The donor layer 151 is formed on the second hole transport layer 131. The donor layer 151 is formed using the highest level occupant molecular orbital energy level of -5.6 eV or less to increase the interfacial energy gap between the donor layer 151 and the acceptor layer 152. As a donor layer forming material, DCV5T, SubPc, DIP, DBP, merocyanine dye, squaraine dye, DTDCTP, and DTS (PTTh2) 2 can be used, for example, DCV5T can be used.

An acceptor layer 152 is formed on the donor layer 151. Acceptor layer 152 comprises C60, C70, [60] PCBM ([6,6] -phenyl-C61-butylic acid methyl ester), and [70] PCBM ([6,6] -phenyl-C71-butyl At least one of lactic acid methyl ester).

The second electrode 171 is formed on the acceptor layer 152. The second electrode 171 may act as a cathode and may be formed using, for example, Al.

Hereinafter, the organic solar cell according to the exemplary embodiment will be described in more detail with reference to non-limiting examples. However, the present invention is not limited to the following examples.

Example  One

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : ReO3  (75:25) / TAPC  Of DCV5T  Of C60  Of BCP  Of Al

As an anode, a 1500-thick ITO glass substrate in which an ITO film was deposited on a glass substrate was used. TAPC and ReO 3 (p-type dopant) were simultaneously deposited on the ITO glass substrate at a molar ratio of 75:25 to form a first hole transport layer having a thickness of 400. TAPC was deposited on the first hole transport layer to form a second hole transport layer having a thickness of 50.

DCV5T was deposited on the second hole transport layer to form a donor layer having a thickness of 70, and C60 was deposited on the donor layer to form an acceptor layer having a thickness of 350.

An organic solar cell was manufactured by depositing BCP on the acceptor layer to form an exciton blocking layer having an thickness of 80, and then depositing Al to form a cathode having a thickness of 1000.

Example  2

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : ReO3  (80:20) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC and ReO 3 were simultaneously deposited in a molar ratio of 80:20 in Example 1.

Example  3

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : ReO3  (85:15) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC and ReO 3 were simultaneously deposited in a molar ratio of 85:15 in Example 1.

Example  4

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : ReO3  (90:10) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC and ReO 3 were simultaneously deposited in a molar ratio of 90:10 in Example 1.

Example  5

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : ReO3  (95: 5) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC and ReO 3 were simultaneously deposited in a molar ratio of 95: 5 in Example 1.

Comparative example  One

An organic solar cell having the following configuration was manufactured:

ITO  / 2- TNATA : ReO3  (75:25) / 2- TNATA  Of DCV5T  Of C60  Of BCP  Of Al

Example 1, except that 2-TNATA (4,4 ′, 4 ″ -tris (N- (2-naphthyl) -N-phenylamino) -tphenylenamine) was used instead of TAPC in Example 1 An organic solar cell was manufactured using the same method as in Example 1.

Comparative example  2

An organic solar cell having the following configuration was manufactured:

ITO  Of NPB : ReO3  (75:25) / NPB  Of DCV5T  Of C60 Of BCP  Of Al

Example 1 was used in the same manner as in Example 1, except that NPB (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was used instead of TAPC. An organic solar cell was prepared.

Comparative example  3

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC  Of TAPC  Of DCV5T  Of C60  Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC single material was used instead of TAPC and ReO3 in Example 1.

Comparative example  4

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : CuI  (75:25) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured by the same method as Example 1, except that CuI was used instead of ReO3 in Example 1.

Comparative example  5

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : WO3  (75:25) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that WO 3 was used instead of ReO 3 in Example 1.

Comparative example  6

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : MoO3  (75:25) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 1, except that MoO 3 was used instead of ReO 3 in Example 1.

Comparative example  7

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : MoO3  (80:20) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 2, except that MoO 3 was used instead of ReO 3 in Example 2.

Comparative example  8

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : MoO3  (85:15) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured by the same method as Example 3, except that MoO 3 was used instead of ReO 3 in Example 3.

Comparative example  9

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : MoO3  (90:10) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured by the same method as Example 4, except that MoO 3 was used instead of ReO 3 in Example 4.

Comparative example  10

An organic solar cell having the following configuration was manufactured:

ITO  Of TAPC : MoO3  (95: 5) / TAPC  Of DCV5T  Of C60 Of BCP  Of Al

An organic solar cell was manufactured in the same manner as in Example 5, except that MoO 3 was used instead of ReO 3 in Example 5.

Evaluation example

The organic solar cells according to Example 1 and Comparative Examples 1 and 2 were measured by using an AM 1.5G solar simulator (Oriel 69911) and a power supply device (Keithley 237), and are shown in FIG. 4 by measuring a relationship between voltage and current density. The difference between the highest level occupant molecular orbital energy level of the second hole transport layer and the highest level occupant molecular orbital energy level of the donor layer (ΔHOMO), voltage (Voc), filling rate (FF), current density (Jsc) and power conversion efficiency ( PCE) was obtained and shown in Table 1.

Table 1 ΔHOMO (eV) V _oc (V) FF J _sc (㎃ / ㎠) PCE (%) Example 1 0.1 1.03 0.57 5.44 3.23 Comparative Example 1 0.6 0.96 0.33 4.37 1.37 Comparative Example 2 0.2 1.03 0.51 4.62 2.41

Referring to Table 1, the organic solar cell according to Example 1 has a ΔHOMO level of 0.1 eV, which is lower than the ΔHOMO value of the organic solar cells according to Comparative Examples 1 and 2, resulting in a higher filling rate and a higher current density. It can be seen that there is a higher tendency.

Referring to FIG. 4, the organic solar cell according to Example 1 does not appear to have a significant decrease in the S-shape compared to the organic solar cell according to Comparative Examples 1 to 2. From this, the organic solar cell using the TAPC and ReO3 in a molar ratio of 75:25 to form the first hole transport layer formed the first hole transport layer using the 2-TNATA and ReO3, NPB and ReO3 in a molar ratio of 75:25. It can be seen that the S-shape is greatly reduced compared to the organic solar cell.

The organic solar cells according to Example 1 and Comparative Examples 3 to 6 were measured using an AM 1.5G solar simulator (Oriel 69911) and a power supply device (Keithley 237) to measure the relationship between voltage and current density, and are shown in FIG. 5. Fermi level of p-type dopant (WF), difference between orbital energy level of highest hole occupant of first hole transport material and Fermi level of p-type dopant (ΔE), voltage (Voc), filling rate (FF), current density ( Jsc) and power conversion efficiency (PCE) are shown in Table 2.

TABLE 2 W _F (eV) ΔE (eV) V _oc (V) FF J _sc (㎃ / ㎠) PCE (%) Example 1 -6.8 1.3 1.03 0.57 5.44 3.23 Comparative Example 3 - - 1.04 0.37 5.39 2.07 Comparative Example 4 -5.8 0.3 1.03 0.45 5.17 2.38 Comparative Example 5 -6.4 0.9 1.07 0.48 5.48 2.81 Comparative Example 6 -6.6 1.1 1.06 0.50 5.41 2.87

Referring to Table 2, the organic solar cell according to Example 1 has a ΔE level of 1.3 eV, which is greater than the ΔE value of the organic solar cells according to Comparative Examples 3 to 6, resulting in a higher filling rate and a higher current density. It can be seen that it shows a high tendency.

5, the lower the Fermi level of the p-type dopant (ReO3 <MoO3 <WO3 <CuI), the tendency of the S-shape generation (Example 1 <Comparative Example 6 <Comparative Example 5 <Comparative Example 4 <Comparative Example 3) decreases. This suggests that when the Fermi level of the dopant is low (e.g., in Example 1), the charge carrier density is increased and the contact resistance at the interface between the first hole transport layer and the first electrode decreases, so that the S-shape does not appear on the voltage-current graph. It can be seen that.

For the organic solar cells according to Examples 1 to 5, the relationship between the voltage and the current density was measured by using an AM 1.5G solar simulator (Oriel 69911) and a power supply device (Keithley 237). , Fill factor (FF), current density (Jsc) and power conversion efficiency (PCE) were calculated and shown in Table 3.

TABLE 3 V _oc (V) FF J _sc (㎃ / ㎠) PCE (%) Example 1 1.03 0.57 5.44 3.23 Example 2 1.03 0.51 5.55 3.1 Example 3 1.04 0.50 5.61 2.93 Example 4 1.04 0.46 5.52 2.61 Example 5 1.04 0.39 5.27 2.14

Referring to FIG. 6, as the content of ReO 3 doped in TAPC increases, the tendency of S-shape generation of the organic solar cell decreases, especially in the case where the first hole transport layer is formed by doping TAO with 25 mol% of ReO 3. You can see that the shape disappears completely.

The organic solar cell according to Comparative Examples 6 to 10 was measured using an AM 1.5G solar simulator (Oriel 69911) and a power supply device (Keithley 237), and the voltage-current density relationship was measured in FIG. , Fill factor (FF), current density (Jsc) and power conversion efficiency (PCE) were calculated and shown in Table 4.

Table 4 V _oc (V) FF J _sc (㎃ / ㎠) PCE (%) Comparative Example 6 1.06 0.50 5.41 2.87 Comparative Example 7 1.05 0.50 5.38 2.83 Comparative Example 8 1.05 0.49 5.45 2.79 Comparative Example 9 1.05 0.47 5.53 2.71 Comparative Example 10 1.04 0.41 5.53 2.37

Referring to FIG. 7, all of the organic solar cells according to Comparative Examples 6 to 10 are observed to have an S-shape. It was observed that the organic solar cell according to Comparative Example 6 had the weakest tendency of S-shape generation but still occurred. From this, the organic solar cell formed by forming a first hole transport layer by doping MoO 3 to 5 mol% to 25 mol% in TAPC still has an S-shape, and the S-shape does not disappear completely even if the doping content of MoO 3 increases. It can be seen that.

Although the present invention has been described with reference to the above embodiments, it is merely illustrative, 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 will be defined by the technical details of the appended claims.

Claims (17)

First electrode A first hole transport layer formed on the first electrode and including a p-type dopant in a first hole transport material A second hole transport layer formed on the first hole transport layer A photoactive layer formed on the second hole transport layer and including a donor layer and an acceptor layer; A second electrode formed on the photoactive layer; The highest occupied molecular orbital energy level of the donor layer is -5.6 eV or less, The highest level occupant molecular orbital energy level of the second hole transport layer is 0 to 0.1 eV higher than the highest level occupant molecular orbital energy level of the donor layer, An organic solar cell having a Fermi level of the p-type dopant lower than the highest level occupant molecular orbital energy level of the first hole transport material. The method of claim 1, The organic solar cell of the p-type dopant comprises rhenium oxide. The method of claim 1, The first hole transport material is an organic solar cell comprising TAPC (1,1-bis [4- [N, N'-di (p-tolyl) amino] phenyl] cyclo hexane). The method of claim 1, The organic solar cell of claim 2, wherein the second hole transport layer comprises the first hole transport material. The method of claim 1, The second hole transport layer includes the first hole transport material, and the first hole transport material is TAPC (1,1-bis [4- [N, N'-di (p-tolyl) amino] phenyl] cyclo Hexane) organic solar cell comprising. The method of claim 1, The organic solar cell of the p-type dopant is 25 mol% relative to the total weight of the first hole transport layer. The method of claim 1, The donor layer is DCV5T (α, α-bis (2,2-dicyanovinyl) -quinquethiophene), SubPc (subphthalocyanine), DIP (diindenoperylene), DBP (tetraphenyl-dibenzoperiflanthene), merocyanine dye, squaraine Squaraine dye, DTDCTP (2-{[2- (5-N, N-di (p-tolyl) aminothiophen-2-yl) -pyrimidin-5-yl] methylene} -malononitrile), and DTS ( PTTh2) 2 (5,5'-bis {(4- (7-hexylthiophen-2-yl) thiophene-2-yl)-[1,2,5] -thiadiazolo [3,4, -c] pyridine}- An organic solar cell comprising at least one of 3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene). The method of claim 1, The acceptor layer comprises C60, C70, [60] PCBM ([6,6] -phenyl-C61-butylic acid methyl ester), and [70] PCBM ([6,6] -phenyl-C71-butylic acid An organic solar cell comprising at least one of methyl ester). The method of claim 1, An organic solar cell in which the donor layer and the second hole transport layer are in contact with each other. The method of claim 1, The organic solar cell of the first electrode comprises ITO. The method of claim 1, An organic solar cell further comprising an exciton blocking layer interposed between the photoactive layer and the second electrode. Forming a first electrode on the substrate Forming a first hole transport layer using a first hole transport material and a p-type dopant on the first electrode, wherein the Fermi level of the p-type dopant is the highest molecular weight orbital energy level of the first hole transport material Lower stage Forming a second hole transport layer on the first hole transport layer Forming a photoactive layer including a donor layer and an acceptor layer on the second hole transport layer, wherein the highest occupied molecular orbital energy level of the donor layer is -5.6 eV or less and occupies the highest level of the second hole transport layer; A molecular orbital energy level is 0 to 0.1 eV higher than the highest occupied molecular orbital energy level of the donor layer, and Forming a second electrode on the photoactive layer; The method of claim 12, A method for producing an organic solar cell using rhenium oxide as the p-type dopant. The method of claim 12, A method of manufacturing an organic solar cell using TAPC as the first hole transport material. The method of claim 12, The second hole transport layer is a method of manufacturing an organic solar cell formed using the first hole transport material. The method of claim 12, The content of the p-type dopant is 25 mol% of the total weight of the first hole transport layer manufacturing method of an organic solar cell. The method of claim 12, The donor layer is a method of manufacturing an organic solar cell formed using at least one of DCV5T, SubPc, DIP, DBP, merocyanine dye, squaraine dye, DTDCTP, and DTS (PTTh ₂ ) ₂ .

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