JP6638293B2 - Hole transport layer material and solar cell using hole transport layer material - Google Patents

Description

  The present invention relates to a hole transport layer material and a solar cell using the hole transport layer material.

  Solar cells generally use elements such as silicon-based, compound semiconductors, and organic semiconductors.In addition to high light-collecting ability, organic and inorganic hybrid types that can be thinned and reduced in cost can be used. Solar cells are attracting attention.

Non-Patent Document 1 discloses a glass substrate with a transparent conductive film, a blocking layer made of a dense titanium dioxide (TiO ₂ ) film, and lead iodide (PbI ₂ ) and methyl as dyes which are excited by light to generate electrons. A hybrid solar cell including a power generation layer formed by adsorbing ammonium iodide (CH ₃ NH ₃ I) on porous titanium dioxide (TiO ₂ ), a hole transport layer, and electrodes is shown. I have.

This power generation layer is manufactured using a two-step process in which PbI ₂ is permeated into the pores of the porous TiO ₂ using a spin coating method, and then immersed in a solution containing CH ₃ NH ₃ I. As a result, crystals of the perovskite dye (CH ₃ NH ₃ PbI ₃ ) are promptly generated, so that the photoelectric conversion efficiency is improved.

Further, as the hole transport layer material used for the hole transport layer, 2,2 ′, 7,7′-tetrakis (N, N′-di-p-methoxyphenylamino) -9, 9'-spirobifluorene (2,2 ', 7,7'-tetrakis (N, N'-di-p-methoxyphenylamine) -9,9'-spirobifluorene (general name "Spiro-OMeTAD"; Is used)). The perovskite dye crystal absorbs light to generate electrons and holes. Holes are transported to the counter electrode by the hole transport layer material, and electrons are generated by repeating a cycle of moving to the photoelectrode.

  Non-Patent Document 2 discloses a solar cell using a polymerized material such as poly (triarylamine) (general name: “PTAA”; hereinafter, this name is used) as a hole transport layer material. Batteries have also been reported.

Burschka, J. et al, Sequential deposition as a route to high-performance perovskite-sensitized solar cells, Nature, 2013.07.10, volume499, p316-319, doi: 10.1038 / nature12340 Jun Hong Noh et al, Chemical Management for Colorful, Efficient, and Stable Inorganic-Organic Hybrid Nanostructured Solar Cells, Nano Letter, 2013, 13 (4), p 1764-1769

  As described above, the hybrid solar cell has a high light-collecting ability and has a high power generation performance even under weak light energy such as in a room, so that it is expected to be used in various environments. On the other hand, Spiro-OMeTAD and PTAA used as hole transport layer materials in the hybrid solar cells of Non-Patent Documents 1 and 2 are inferior in durability and lose their functions in a few days when left in the air. There was a problem. This is because Spiro-OMeTAD and PTAA have a bulky molecular structure, making it difficult to obtain electrical contact between the molecules. Therefore, it functions as a hole transport layer by adding a cobalt complex or the like as a dopant. However, the performance of the solar cell changes depending on the amount of the dopant added and the degree of mixing (concentration distribution), and the same function is stably exhibited. It was difficult to make it.

  For example, when Spiro-OMeTAD is laminated as a hole transport layer material, a gap is generated between adjacent molecules due to the above-described molecular structure, and various molecules may be taken into the gap. Therefore, when producing a hole transport layer by Spiro-OMeTAD, for example, Spiro-OMeTAD is mixed with a dopant or the like, and this mixture is dissolved in a solvent, applied, and then heated to evaporate the solvent. However, when a solvent molecule is taken into the gap between Spiro-OMeTAD molecules, it is difficult to completely remove the molecule, and there is a problem that the performance of the solar cell is not stable due to this. In addition, in the case where the solar cell is constructed as a solar cell, there is a possibility that water molecules in the environment may enter the gaps during use and cause deterioration in solar cell performance and durability.

  Further, the synthesis of Spiro-OMeTAD and PTAA requires complicated reaction steps and many steps, and many steps are required for purification. As a result, the price of Spiro-OMeTAD and PTAA was increased. Furthermore, in the case of a solar cell using Spiro-OMeTAD and PTAA as a hole transport layer material, the number of steps required for fabrication has increased, leading to an increase in price.

  In view of the above-mentioned problems of the related art, it has been demanded to provide a hole transport layer material having excellent hole transportability, and to provide a hole transport layer material having excellent durability. Further, it has been required to provide the hole transport layer material at low cost. Further, it has been required to provide a solar cell having high battery performance at low cost.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, a hole transport layer material having a phthalocyanine skeleton in the molecule and having a specific substituent on the outer periphery of the phthalocyanine skeleton has a high planarity of the molecule, It has been found that when molecules are superimposed, good electrical connection between molecules such as a π-conjugated system can be ensured, and that they have excellent hole transport properties. In addition, it has been found that the hole transport layer material has excellent properties in terms of durability. When the hole transport layer material is used for a hole transport layer of a hybrid solar cell or the like, the hole transport layer material exhibits excellent hole transport properties, exhibits excellent battery performance in an initial experiment, and also has a durability. They found that they were excellent, and completed the present invention.

（一般式（Ｉ）において、
Ｍは、亜鉛（Zn）、銅（Cu）、コバルト（Co）、鉄（Fe）、ニッケル（Ni）、鉛（Pb）、マンガン（Mn）又はスズ（Sn）であり、
R^1a及びR^1bは互いに独立で、一方が下記置換基（Ａ）〜（Ｉ）から選択され、他方は水素であり、
R^2a及びR^2bは互いに独立で、一方が下記置換基（Ａ）〜（Ｉ）から選択され、他方は水素であり、
R^3a及びR^3bは互いに独立で、一方が下記置換基（Ａ）〜（Ｉ）から選択され、他方は水素であり、
R^4a及びR^4bは互いに独立で、一方が下記置換基（Ａ）〜（Ｉ）から選択され、他方は水素であり、
R^1a又はR^1bで選択される置換基、R^2a又はR^2bで選択される置換基、R^3a又はR^3bで選択される置換基、R^4a又はR^4bで選択される置換基は同一である。

ここで、前記置換基（Ａ）のX¹が、C₆〜C₈アルキル基であり、前記置換基（Ｂ）のX²が、C₆〜C₈アルキル基であり、前記置換基（Ｃ）のX³が、C₆〜C₈アルキル基であり、前記置換基（Ｄ）のX⁴が、C₆〜C₈アルキル基であり、前記置換基（Ｅ）のX⁵及びX⁶が、同一でC₆〜C₈アルキル基であり、前記置換基（Ｆ）のX⁷及びX⁸が、同一でC₄〜C₆アルキル基又はC₁〜C₃アルコキシ基であり、前記置換基（Ｇ）のX⁹が、C₄〜C₆アルキル基又はジフェニルアミノ基であり、前記置換基（Ｉ）のX¹⁰が、C₄〜C₆アルキル基である。）

（一般式（ＩＩ）、（ＩＩＩ）において、
Ｍは、亜鉛（Zn）、銅（Cu）、コバルト（Co）、鉄（Fe）、ニッケル（Ni）、鉛（Pb）、マンガン（Mn）又はスズ（Sn）であり、
R⁵、R⁶、R⁷、R⁸、R⁹、R¹⁰、R¹¹、及びR¹²は同一の置換基であり、下記の（Ｊ）〜（Ｎ）から選択される。

ここで、前記置換基（Ｊ）のX¹¹が、C₁〜C₆アルキル基であり、前記置換基（Ｋ）のX¹²が、C₄〜C₆アルキル基、C₁〜C₃アルコキシ基、又はジフェニルアミノ基であり、前記置換基（Ｌ）のX¹³及びX¹⁴が、同一でC₁〜C₃アルコキシ基であり、前記置換基（Ｍ）のX¹⁵が、C₄〜C₆アルキル基であり、前記置換基（Ｎ）のX¹⁶はC₁〜C₃アルコキシ基、又は水素である。） A feature of the hole transport layer material according to the present invention is that it is a compound selected from the following general formulas (I) to (III).

(In the general formula (I),
M is zinc (Zn), copper (Cu), cobalt (Co), iron (Fe), nickel (Ni), lead (Pb), manganese (Mn) or tin (Sn);
R ^1a and R ^1b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^2a and R ^2b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^3a and R ^3b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^4a and R ^4b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
The substituent selected by R ^1a or R ^1b , the substituent selected by R ^2a or R ^2b , the substituent selected by R ^3a or R ^3b , the substituent selected by R ^4a or R ^4b are the same. is there.

Here, X ¹ of the substituent (A) is a C ₆ -C ₈ alkyl group, X ² of the substituent (B) is a C ₆ -C ₈ alkyl group, and the substituent (C ) is X ³ of a C ₆ -C ₈ alkyl group, wherein the X ⁴ substituent (D), a C ₆ -C ₈ alkyl group, X ⁵ and X ⁶ of the substituent (E) , identical with a C ₆ -C ₈ alkyl group, X ⁷ and X ⁸ of the substituent (F) is a C ₄ -C ₆ alkyl or C ₁ -C ₃ alkoxy group in the same, said substituents X ^{9 in} (G) is a C ₄ -C ₆ alkyl group or diphenylamino group, and X ^{10 in the} substituent (I) is a C ₄ -C ₆ alkyl group. )

(In the general formulas (II) and (III),
M is zinc (Zn), copper (Cu), cobalt (Co), iron (Fe), nickel (Ni), lead (Pb), manganese (Mn) or tin (Sn);
R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are the same substituent and are selected from the following (J) to (N).

Here, X ¹¹ of the substituent (J) is a C ₁ -C ₆ alkyl group, and X ¹² of the substituent (K) is a C ₄ -C ₆ alkyl group or a C ₁ -C ₃ alkoxy group. Or X ¹³ and X ¹⁴ of the substituent (L) are the same C ₁ -C ₃ alkoxy group, and X ^{15 of the} substituent (M) is C ₄ -C ₆ X ¹⁶ of the substituent (N) is a C ₁ -C ₃ alkoxy group or hydrogen. )

  According to the above configuration, it is possible to provide a hole transport layer material having an excellent hole transport property, which can stably and efficiently capture and move holes. Specifically, phthalocyanine, which forms the skeleton of the hole transport layer material of the present configuration, is a cyclic structure having high planarity, and forms a cyclically continuous π electron cloud. The π electron clouds overlap each other between phthalocyanine molecules, and the phthalocyanine molecules are stabilized in an arrangement in which a plurality of flat plates are stacked (referred to as “π-π stacking”). Thereby, the phthalocyanine can move holes in the direction in which the flat plates are stacked, and can exhibit good hole transportability.

  Further, the material of the hole transport layer having this configuration also has excellent characteristics in terms of long-term durability. The above-mentioned π-π stacking state in phthalocyanine is extremely stable and strong, and external oxidation (emission of electrons) and reduction (injection of electrons) can be diffused by multiple molecules, As a stable state, and has high weather resistance. Since the hole transport layer material of this configuration has such a phthalocyanine skeleton having weather resistance, it has a characteristic of high durability without being decomposed by light irradiation or temperature and humidity.

  In addition, since the hole transport layer material of this configuration has high planarity as described above, no voids are generated between molecules, and other molecules that may be a factor to reduce hole transportability are mixed between molecules. Can be prevented. In addition, electrical connection between molecules can be secured. This makes it possible to stabilize the hole transport performance and exhibit excellent performance in terms of durability.

  The hole transport layer material of this configuration has excellent characteristics in terms of solubility in a solvent. Phthalocyanine has a very low solubility in a solvent due to strong interaction between molecules due to the aforementioned π-π stacking, and its use has been limited. However, the hole transport layer material of this configuration was bulky on the outer periphery of the phthalocyanine skeleton so as not to hinder π-π stacking, and a substituent was uniformly introduced in order to improve solubility in a solvent. As a result, the hole transport layer material of this configuration becomes soluble in a solvent such as chlorobenzene, and can be used in place of a compound having a spiro ring structure such as a general-purpose Spiro-OMeTAD.

  In the hole transport layer material having this configuration, the electrical characteristics and the solubility in a solvent can be controlled by changing the substituent and the central metal introduced to the outer periphery of the phthalocyanine skeleton. Thereby, a hole transport layer material having higher performance can be provided.

  The hole transport layer material of this configuration can be synthesized simply and inexpensively. The hole transport layer material of this configuration can be synthesized in fewer steps and is easier to purify than conventional compounds with a spiro ring structure such as Spiro-OMeTAD, so the cost required for synthesis is reduced. can do.

  As described above, the hole transport layer material having this configuration has excellent characteristics, and thus can be suitably used as the hole transport layer material of the solar cell 10.

Another characteristic configuration of the present invention is a compound represented by the general formula (I),
The substituent (A) is a 5-hexyl-thiophen-2-yl group or a 5- (2-ethylhexyl) -thiophen-2-yl group;
The substituent (B) is a 5- (hexylsulfanyl) -thiophen-2-yl group,
The substituent (C) is a 5′-hexyl-2,2′-bithiophen-5-yl group or a 5 ′-(2-ethylhexyl) -2,2′-bithiophen-5-yl group,
The substituent (D) is a 5-hexyl-thieno [3,2-b] thiophen-2-yl group or a 5- (2-ethylhexyl) -thieno [3,2-b] thiophen-2-yl group And
The substituent (E) is a 5,5 ″ -dihexyl-2,2 ′: 3 ′, 2 ″ -terthiophen-5′-yl group;
The substituent (F) is a bis (4-hexylphenyl) amino group, a bis (4-methoxyphenyl) amino group, or a bis (4-tert-butylphenyl) amino group;
The substituent (G) is a 4-tert-butylphenyl group or a 4- (diphenylamino) phenyl group;
The substituent (H) is a 2,6-diphenylphenoxy group,
Wherein the substituent (I) is a tert-butyl group.

  According to this configuration, each of the four imidazole rings located on the outer periphery of the phthalocyanine skeleton has one bulk at the β-position of the benzene ring portion so as not to hinder intermolecular π-π stacking, and The hole transport layer material can be provided as a phthalocyanine derivative into which a suitable substituent is introduced for improving the solubility. This makes it possible to particularly suitably control the electrical characteristics and the solubility in a solvent, and to provide a hole transport layer material having high performance.

Another feature is the compound represented by the general formula (II):
The substituent (J) is a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, or a hexyloxy group;
The substituent (K) is a 4-methoxyphenyl group, a 4-tert-butylphenyl group, or a 4- (diphenylamino) phenyl group;
The substituent (L) is a 3,4-dimethoxyphenyl group,
The substituent (M) is a (4-tert-butylphenyl) sulfanyl group,
The substituent (N) is a 2,6-diphenylphenoxy group or a 5-methoxy-2,6-diphenylphenoxy group.

  According to this configuration, the two benzene ring portions of the four imidazole rings located at the outer periphery of the phthalocyanine skeleton are each made to be bulky to such an extent that π-π stacking between molecules is not hindered, and to be soluble in a solvent. The hole transport layer material can be provided as a phthalocyanine derivative into which a particularly suitable substituent has been introduced in order to improve the property. This makes it possible to particularly suitably control the electrical characteristics and the solubility in a solvent, and to provide a hole transport layer material having high performance.

Another characteristic structure is a compound represented by the general formula (III):
The substituent (J) is a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, or a hexyloxy group;
The substituent (K) is a 4-methoxyphenyl group, a 4-tert-butylphenyl group, or a 4- (diphenylamino) phenyl group;
The substituent (L) is a 3,4-dimethoxyphenyl group,
The substituent (M) is a (4-tert-butylphenyl) sulfanyl group,
Wherein the substituent (N) is a 5-methoxy-2,6-diphenylphenoxy group.

  According to the present configuration, according to the present configuration, the bulk is increased so as not to hinder the intermolecular π-π stacking at each of the two α-positions of the benzene ring portion of the four imidazole rings located on the outer periphery of the phthalocyanine skeleton. In addition, the hole transport layer material can be provided as a phthalocyanine derivative into which a substituent that is particularly suitable for improving solubility in a solvent is introduced. This makes it possible to particularly suitably control the electrical characteristics and the solubility in a solvent, and to provide a hole transport layer material having high performance.

Another structure lies in that it is a compound represented by the following general formula (IV).

  According to this configuration, the hole transport layer is formed as a phthalocyanine derivative in which a hexylthiophene ring is uniformly introduced as a substituent at each of the β-positions of the benzene ring portions of the four imidazole rings located at the outer periphery of the phthalocyanine skeleton. Material can be provided. The substituent is bulky to the extent that π-π stacking between molecules of the hole transport layer material is not hindered, and is particularly suitable for improving solubility in a solvent. Can be controlled particularly suitably, and further, a hole transport layer material having high performance can be provided.

  The characteristic configuration of the solar cell according to the present invention includes a substrate having a transparent conductive film, a blocking layer that transfers electrons to the transparent conductive film, and prevents reverse electron transfer, and a dye that is excited by light to generate the electrons. A power generation layer formed by being adsorbed to a porous semiconductor, a hole generated from the dye passes through, a hole transport layer having the hole transport layer material, and a stacked body laminated in this order; It comprises a photoelectrode that emits electrons, and an electrode composed of a counter electrode provided on the surface of the hole transport layer.

  By using a hole transport layer material having excellent hole transport properties for the hole transport layer of a solar cell as in the present configuration, the photoelectric conversion efficiency is improved. Furthermore, the excellent durability of the hole transport layer material increases the durability of the solar cell. In particular, since perovskite dye crystals, which are liable to deteriorate in performance due to moisture absorption, are coated with a hole-transporting layer material having weather resistance, further long-term durability can be expected. As described above, the hole transport layer having the hole transport layer material having excellent characteristics can improve the battery performance of the solar cell. In addition, by using a hole transport layer material that can be synthesized at a low cost, it is possible to reduce the cost of the solar cell itself.

It is a schematic cross section of a hybrid type solar cell. FIG. 3 is a schematic view of the hybrid solar cell from above. FIG. 3 is an explanatory diagram of power generation of a hybrid solar cell. It is explanatory drawing which shows the preparation procedure of a hybrid type solar cell. It is a figure which shows the suitable example of a hole transport layer material. It is a figure which shows the suitable example of a hole transport layer material. It is a figure which shows the suitable example of a hole transport layer material. FIG. 3 is a view showing a synthesis scheme of a hole transport layer material. 3 shows a performance curve of a solar cell using Sym-HT-PcH as a hole transport layer material. 5 shows a performance curve of a solar cell using Spiro-OMeTAD as a hole transport layer material (Comparative Example). It is a graph which shows the result of having compared the durability of the solar cell in the case of Sym-HT-PcH and Spiro-OMeTAD as a hole transport layer material.

  Hereinafter, an embodiment of a hybrid solar cell 10 (an example of a solar cell; hereinafter, referred to as “solar cell 10”) using a hole transport layer material according to an embodiment of the present invention will be described with reference to the drawings. I do. The solar cell 10 is configured to include a perovskite dye formed of an organic / inorganic hybrid compound. However, without being limited to the following embodiments, various modifications can be made without departing from the scope of the invention.

(Basic configuration of solar cell according to this embodiment)
As shown in FIGS. 1 and 2, a solar cell 10 according to the present embodiment is provided with a substrate 2 having a transparent substrate 21 and a transparent conductive film 22, and provided on the substrate 2, and passes electrons to the transparent conductive film 22. A blocking layer 3 that separates the hole transport layer 5 from the transparent conductive film 22 to prevent recombination of electrons and holes (reverse electron transfer); and a blocking layer 3 provided on the blocking layer 3 to excite electrons by light. The laminated body 11 composed of the power generation layer 4 formed by adsorbing the generated dye 44 on the porous semiconductor 41 and the hole transport layer 5 provided on the power generation layer 4 and through which holes generated by the dye 44 pass is used. Have. The electrode 6 includes a photoelectrode 61 provided on the surface of the blocking layer 3 and emitting electrons through the transparent conductive film 22 and a counter electrode 62 provided on the surface of the hole transport layer 5 and receiving electrons. It has. The arrangement of the electrode 6 is not particularly limited as long as it can transfer electrons, for example, by forming a photoelectrode 61 by connecting a conductive wire to the transparent conductive film 22. Further, in order to enhance the durability of the solar cell 10, the counter electrode 62 may be protected by the transparent substrate 21 or the like.

  The transparent substrate 21 is made of a material having light transmittance. For example, a transparent glass substrate, a frosted glass-like translucent glass substrate, a transparent resin substrate, or the like can be used. For the transparent conductive film 22, for example, fluorine-doped tin oxide (FTO), tin oxide (TO), tin-doped indium oxide (ITO), zinc oxide (ZnO), and aluminum-doped zinc oxide (AZO) can be used. .

The blocking layer 3 and the porous semiconductor 41 are preferably made of a metal oxide, such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), tin dioxide (SnO ₂ ), and oxidized metal. Aluminum (Al ₂ O ₃ ) or the like is used. In particular, it is preferable to constitute the sintered body of titanium dioxide (TiO ₂ ) which can secure a large surface area for adsorbing the dye 44. In addition, the blocking layer 3 is formed so as to partially extend to the transparent conductive film 22 to partition the transparent conductive film 22. Furthermore, the blocking layer 3 forms the dense insulating layer 31 so that electrons can pass in the laminating direction but are hardly moved in the lateral direction. That is, the electrons that have entered from the blocking layer 3 move smoothly in the laminating direction of the transparent conductive film 22 and are supplied to the photoelectrode 61, and the movement to the counter electrode 62 is prevented by the insulating layer 31. .

The dye 44 is formed by reacting a compound (PbX ₂ , X = halogen element) composed of lead and a halogen element X with methylammonium iodide (CH ₃ NH ₃ I: hereinafter referred to as MAI). Is done. Specifically, a solution 42 containing lead and a halogen element X is permeated and dried in the pores of the porous semiconductor 41, and then immersed in a mixed solution 43 of MAI, and a perovskite dye (X = I In this case, crystals of CH ₃ NH ₃ PbI ₃ ) are rapidly formed. As the halogen element X, iodine, bromine, chlorine or the like can be used, but it is preferable to use iodine having high form stability.

  The hole transport layer 5 uses a hole transport layer material described later. For the electrode 6, for example, a simple substance or alloy of a metal such as gold, platinum, silver, or copper, or an oxide conductor such as fluorine-doped tin oxide (FTO) or tin-doped indium oxide (ITO) can be used.

  Here, the principle of power generation by the solar cell 10 will be described with reference to FIG. When light such as sunlight or room light enters the transparent substrate 21, the incident light transmits through the substrate 2 and the blocking layer 3 without being absorbed, and reaches the power generation layer 4 in large part. When the incident light that has reached the power generation layer 4 irradiates the dye 44, the dye 44 absorbs light energy and is excited. When the energy level of the dye 44 becomes higher than the conduction charge level of the metal oxide as the porous semiconductor 41 by a predetermined level or more due to this excitation, electrons are injected from the dye 44 into the porous semiconductor 41. The injected electrons are collected by the photoelectrode 61 via the blocking layer 3.

  On the other hand, the holes generated by the dye 44 reach the counter electrode 62 via the hole transport layer 5 and recombine there with the electrons passing through the external load 7. That is, since a potential gradient is generated between the photoelectrode 61 and the counter electrode 62, power can be supplied by connecting the external load 7 between both electrodes.

(Procedure for manufacturing solar cell according to present embodiment)
A procedure for manufacturing the solar cell 10 according to the present embodiment will be described with reference to FIG. However, without being limited to the following embodiments, various modifications can be made without departing from the scope of the invention.

First, the transparent conductive film 22 is formed on the transparent substrate 21 to manufacture the substrate 2. The transparent conductive film 22 is laminated on the transparent substrate 21 by, for example, CVD (Chemical Vapor Deposition) or sputtering. Next, the transparent conductive film 22 is partially removed by laser scribing to form a concave portion 221 in which the insulating layer 31 is to be formed, and then the substrate is washed. Next, a blocking layer 3 is formed on the entire surface of the substrate 2 by ALD (atomic layer deposition), SPD (spray pyrolysis), or the like. The blocking layer is preferably formed as a TiO ₂ dense layer. Next, a porous semiconductor 41 as a nanoparticle sintered layer is formed near the center of the masked substrate 2 and blocking layer 3. Preferably formed as a porous layer of _{TiO 2 (p-TiO 2)} . This porous semiconductor 41 is obtained by diluting the nanoparticle paste with a solvent, for example, applying and drying by spin coating at a rotation speed of 4000 rpm to 6000 rpm, removing the masking, heating at 450 ° C. to 550 ° C., and sintering. It is formed.

For example, an N, N-dimethylformamide solution 42 of lead iodide (PbI ₂ ) is prepared, dropped onto the porous semiconductor 41, and then, for example, spin-coated at a rotation speed of 5000 to 8000 rpm to form pores (p-TiO _2). ) Infiltrate inside and remove excess solution. Dry at 60 ° C to 120 ° C (preferably 70 ° C to 90 ° C) to form a PbI ₂ layer.

Porous semiconductor in which substrate 2, blocking layer 3, and lead iodide have permeated isopropyl alcohol solution 43 (2 to 20 mg / ml) of methylammonium iodide (CH ₃ NH ₃ I, sometimes referred to as “MAI”) 41 is immersed at 0 ° C. to 80 ° C. (preferably at room temperature) (MAI immersion method). The dye 44 [(CH ₃ NH ₃ ) PbI ₃ ] is formed as a perovskite layer by reaction between PbI ₂ and MAI inside and above the pores of the porous semiconductor 41, and then the mixture is irrigated with a pure isopropyl alcohol solution. (Preferably 70 ° C to 100 ° C).

The hole transport layer material according to the present embodiment is prepared, for example, as a chlorobenzene solution of 60 to 90 mg / ml (including some additives). This is dropped, an excess solution is removed by spin coating, and the hole transport layer 5 is formed by drying. The steps from the formation of the _two PbI layers to the formation of the hole transport layer 5 are preferably performed in a dry nitrogen atmosphere such as a glove box. Finally, a thin film of gold or the like is adhered to the surface of the blocking layer 3 and the hole transport layer 5 by a vacuum deposition method or the like to form the electrode 6.

In the above-described preparation procedure, the crystal growth of the perovskite dye as the dye 44 is controlled in two steps, but this may be performed in one step. For example, a perovskite ((CH ₃ NH ₃ ) PbI ₃ ) solution is permeated into the pores of the porous semiconductor 41 by spin coating. Toluene is dropped during spinning to precipitate microcrystals and mirror-finish the surface (negative solvent precipitation method). Subsequently, the hole transport layer 5 may be formed using the hole transport layer material according to the present embodiment.

(Hole transport layer material according to the present embodiment)
The hole transport layer material according to this embodiment has a phthalocyanine skeleton as the central structure. Phthalocyanine is a huge cyclic structure in which four isoindoles are crosslinked via a nitrogen atom, and forms a metal phthalocyanine coordinated around a metal element. In the hole transport layer material according to the present embodiment, a substituent is introduced on the outer periphery of the phthalocyanine skeleton in order to obtain solubility in a solvent and improve electrical characteristics. The substituents are preferably introduced evenly around the phthalocyanine skeleton, and are particularly preferably constructed as symmetrical.

  The characteristic configuration of the hole transport layer material according to this embodiment is a compound selected from the following general formulas (I) to (II). The compound represented by the general formula (I) has a structure in which a substituent is uniformly introduced into one of the four indole rings constituting the phthalocyanine skeleton at the β-position of each benzene ring portion. That is, a substituent is introduced at one of the 2- or 3-position, one of the 9- or 10-position, one of the 16- or 17-position, and one of the 23- or 24-position of the phthalocyanine ring. The compound represented by the general formula (II) has a structure in which substituents are evenly introduced at two positions at the β-position of each benzene ring portion in four indole rings, and the 2-, 3-, and 9-positions of a phthalocyanine ring are obtained. Substituents are introduced at positions 10, 10, 16, 17, 23 and 24. The general formula (III) has a structure in which a substituent is introduced evenly at two positions at the α-position, and is at positions 1, 4, 8, 11, 15, 15, 18, 22, and 25 of the phthalocyanine ring. A substituent is introduced at the position. 5 to 7 show typical examples of the hole transport layer material according to the present embodiment. However, it is not limited to this.

  The hole transport layer material according to this embodiment is configured as a metal phthalocyanine complex in which a metal element coordinates at the center. Therefore, in the general formulas (I) to (III), M is a metal atom, a metal oxide or a metal halide, preferably zinc (Zn), copper (Cu), cobalt (Co), iron (Fe ), Nickel (Ni), lead (Pb), manganese (Mn) or tin (Sn). Particularly preferred is zinc.

  In the hole transport layer material according to the present embodiment, a substituent is introduced on the outer periphery of the phthalocyanine skeleton in order to obtain solubility in a solvent and improve electrical characteristics. Preferred substituents are shown below.

（ここで、前記置換基（Ａ）のX¹が、C₆〜C₈アルキル基であり、前記置換基（Ｂ）のX²が、C₆〜C₈アルキル基であり、前記置換基（Ｃ）のX³が、C₆〜C₈アルキル基であり、前記置換基（Ｄ）のX⁴が、C₆〜C₈アルキル基であり、前記置換基（Ｅ）のX⁵及びX⁶が、同一でC₆〜C₈アルキル基であり、前記置換基（Ｆ）のX⁷及びX⁸が、同一でC₄〜C₆アルキル基又はC₁〜C₃アルコキシ基であり、前記置換基（Ｇ）のX⁹が、C₄〜C₆アルキル基又はジフェニルアミノ基であり、前記置換基（Ｉ）のX¹⁰が、C₄〜C₆アルキル基である。） In the general formula (I),
R ^1a and R ^1b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^2a and R ^2b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^3a and R ^3b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
R ^4a and R ^4b are independent of each other, one is selected from the following substituents (A) to (I), the other is hydrogen,
The substituent selected by R ^1a or R ^1b , the substituent selected by R ^2a or R ^2b , the substituent selected by R ^3a or R ^3b , the substituent selected by R ^4a or R ^4b are the same. is there.

(Where X ¹ of the substituent (A) is a C ₆ -C ₈ alkyl group, X ² of the substituent (B) is a C ₆ -C ₈ alkyl group, and the substituent ( X ³ of C) is a C ₆ -C ₈ alkyl group, wherein X ⁴ substituent (D) is a C ₆ -C ₈ alkyl group, X ⁵ and X ⁶ of the substituent (E) Are the same C ₆ -C ₈ alkyl groups, and X ⁷ and X ⁸ of the substituent (F) are the same C ₄ -C ₆ alkyl groups or C ₁ -C ₃ alkoxy groups, X ^{9 of the} group (G) is a C ₄ -C ₆ alkyl group or a diphenylamino group, and X ¹⁰ of the substituent (I) is a C ₄ -C ₆ alkyl group.)

The C ₆ -C ₈ alkyl group in the substituent (A) may be linear or branched. Particularly preferred is a hexyl group or a 2-ethylhexyl group. Alkyl chains of C ₆ -C ₈ alkyl scan phenyl group in the substituent (B) may be either a separate linear and branched. Preferably, it is a hexyl chain. The C ₆ -C ₈ alkyl group in the substituent (C) may be linear or branched. Preferably, it is a hexyl group or a 2-ethylhexyl group. The C ₆ -C ₈ alkyl group in the substituent (D) may be linear or branched. Preferably, it is a hexyl group or a 2-ethylhexyl group. The C ₆ -C ₈ alkyl group in the substituent (E) may be linear or branched. Preferably, it is a hexyl group. The alkyl group of C ₄ -C ₆ in the substituent (F) may be either a separate linear and branched. Preferably, it is a hexyl group or a t-butyl group. Further, the alkyl chain of the C ₁ -C ₃ alkoxy group may be linear or branched. Preferably, it is a methyl chain. The C ₄ -C ₆ alkyl group in the substituent (G) may be linear or branched. Preferably, it is a t-butyl group. The C ₄ -C ₆ alkyl group in the substituent (G) may be linear or branched. Preferably, it is a t-butyl group.

Here, the C ₁ -C ₃ alkyl group is an alkyl group having ₁ to ₃ carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, and an isopropyl group. The C ₄ -C ₆ alkyl group is an alkyl group having ₄ to ₆ carbon atoms, specifically, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, Isopentyl group, neopentyl group, t-pentyl group, s-pentyl group, 2-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, n-hexyl group, isohexyl group, neohexyl group, t-hexyl group, Examples thereof include a 2,2-dimethylbutyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, and a 1-propylpropyl group. The C ₆ -C ₈ alkyl group, an alkyl group having a carbon number of 6-8, n-hexyl group, isohexyl group, neohexyl group, t-hexyl group, 2,2-dimethylbutyl group, 2-methylpentyl Group, 3-methylpentyl group, 1-ethylbutyl group, 2-ethylbutyl group, 1-propylpropyl group, n-heptyl group, isoheptyl group, s-heptyl group, t-heptyl group, 2,2-dimethylpentyl group, 3,3-dimethylpentyl group, 1-methylhexyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 1-ethylpentyl group, 2-ethylpentyl group, 3-ethylpentyl group, 1-propylbutyl group, 2-propylbutyl group, n-octyl group, isooctyl group, t-octyl group, neooctyl group, 2,2-dimethylhexyl group, 3,3-dimethylhexyl group, 4,4-dimethylhexyl Group, 1-methylheptyl group, 2-methylheptyl group , 3-methylheptyl, 4-methylheptyl, 5-methylheptyl, 1-ethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 1-propylpentyl, 2-propylpentyl And a 3-propylpentyl group. The C ₁ -C ₆ alkyl group is an alkyl group having 1 to 6 carbon atoms, and specific alkyl groups are as described above. Note that “n” is an abbreviation for “normal”, “s” is an abbreviation for “sec” and “secondery”, and “t” is an abbreviation for “tert” and “tertiary”. The same applies to an alkyl chain.

Preferably, but not limited to, in the general formula (I),
The substituent (A) is a 5-hexyl-thiophen-2-yl group or a 5- (2-ethylhexyl) -thiophen-2-yl group;
The substituent (B) is a 5- (hexylsulfanyl) -thiophen-2-yl group,
The substituent (C) is a 5′-hexyl-2,2′-bithiophen-5-yl group or a 5 ′-(2-ethylhexyl) -2,2′-bithiophen-5-yl group,
The substituent (D) is a 5-hexyl-thieno [3,2-b] thiophen-2-yl group or a 5- (2-ethylhexyl) -thieno [3,2-b] thiophen-2-yl group And
The substituent (E) is a 5,5 ″ -dihexyl-2,2 ′: 3 ′, 2 ″ -terthiophen-5′-yl group;
The substituent (F) is a bis (4-hexylphenyl) amino group, a bis (4-methoxyphenyl) amino group, or a bis (4-tert-butylphenyl) amino group;
The substituent (G) is a 4-tert-butylphenyl group or a 4- (diphenylamino) phenyl group;
The substituent (H) is a 2,6-diphenylphenoxy group,
The substituent (I) is a tert-butyl group.

ここで、置換基（Ｊ）のX¹¹が、C₁〜C₆アルキル基であり、置換基（Ｋ）のX¹²が、C₄〜C₆アルキル基、C₁〜C₃アルコキシ基、又はジフェニルアミノ基であり、置換基（Ｌ）のX¹³及びX¹⁴が、同一でC₁〜C₃アルコキシ基であり、置換基（Ｍ）のX¹⁵が、C₄〜C₆アルキル基であり、置換基（Ｎ）のX¹⁶が、C₁〜C₃アルコキシ基、又は水素である。） In the general formulas (II) and (III),
R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² are the same substituent and are selected from the following (J) to (N).

Here, X ¹¹ of the substituent (J) is a C ₁ -C ₆ alkyl group, and X ¹² of the substituent (K) is a C ₄ -C ₆ alkyl group, a C ₁ -C ₃ alkoxy group, or A diphenylamino group, X ¹³ and X ¹⁴ of the substituent (L) are the same and are a C ₁ -C ₃ alkoxy group, and X ¹⁵ of the substituent (M) is a C ₄ -C ₆ alkyl group. And X ^{16 of} the substituent (N) is a C ₁ -C ₃ alkoxy group or hydrogen. )

The C ₁ -C ₆ alkyl group in the substituent (J) may be linear or branched. Preferably, it is a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a hexyl group. The C ₄ -C ₆ alkyl group in the substituent (K) may be linear or branched. Preferably, it is a tert-butyl group. The alkyl chain of the C ₁ -C ₃ alkoxy group may be linear or branched. Preferably, it is a methyl chain. The alkyl chain of the C ₁ -C ₃ alkoxy group in the substituent (L) may be linear or branched. Preferably, it is a methyl chain. The C ₄ -C ₆ alkyl group in the substituent (M) may be linear or branched. Preferably, it is a tert-butyl group. The alkyl chain of the C ₁ -C ₃ alkoxy group in the substituent (N) may be linear or branched. Preferably, it is a methyl chain.

Preferably, in the compound represented by the general formula (II), although not limited thereto,
The substituent (J) is a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, or a hexyloxy group;
The substituent (K) is a 4-methoxyphenyl group, a 4-tert-butylphenyl group, or a 4- (diphenylamino) phenyl group;
The substituent (L) is a 3,4-dimethoxyphenyl group,
The substituent (M) is a (4-tert-butylphenyl) sulfanyl group,
The substituent (N) is a 2,6-diphenylphenoxy group or a 5-methoxy-2,6-diphenylphenoxy group

Preferably, in the compound represented by the general formula (III), the compound is not limited thereto.
The substituent (J) is a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, or a hexyloxy group;
The substituent (K) is a 4-methoxyphenyl group, a 4-tert-butylphenyl group, or a 4- (diphenylamino) phenyl group;
The substituent (L) is a 3,4-dimethoxyphenyl group,
The substituent (M) is a (4-tert-butylphenyl) sulfanyl group,
The substituent (N) is a 5-methoxy-2,6-diphenylphenoxy group.

（一般式（Ｖ）において、
R^13a及びR^13bは互いに独立で、一方が下記置換基（Ｏ）であり、他方は水素であり、
R^14a及びR^14bは互いに独立で、一方が下記置換基（Ｏ）であり、他方は水素であり、
R^15a及びR^15bは互いに独立で、一方が下記置換基（Ｏ）であり、他方は水素であり、
R^16a及びR^16bは互いに独立で、一方が下記置換基（Ｏ）であり、他方は水素である。

[Preferred example of hole transport layer material according to present embodiment]
Preferred examples of the hole transport layer material according to this embodiment are shown below as general formula (V). In the description, the hole transport layer material may be referred to as “Sym-HT-PcH”. The compound represented by the general formula (IV) coordinates zinc as a central metal, and introduces a hexylthiophene ring as a substituent at each of the β-positions of the benzene ring portions of four indole rings serving as the outer skeleton of the phthalocyanine ring. It is composed. That is, a hexylthiophene ring is introduced at one of the 2- or 3-position, one of the 9- or 10-position, one of the 16- or 17-position, and one of the 23- or 24-position of the phthalocyanine ring.

(In the general formula (V),
R ^13a and R ^13b are independent of each other, one is the following substituent (O), the other is hydrogen,
R ^14a and R ^14b are independent of each other, one is the following substituent (O), the other is hydrogen,
R ^15a and R ^15b are independent of each other, one is the following substituent (O), the other is hydrogen,
R ^16a and R ^16b are independent of each other, one is a substituent (O) shown below, and the other is hydrogen.

Among the compounds represented by the general formula (V), compounds represented by the following general formula (IV) are particularly preferred and exemplified.

[Synthesis method of hole transport layer material according to this embodiment]
The method for synthesizing the hole transport layer material according to this embodiment can be easily synthesized with reference to the synthesis method described in Example 1 below. Example 1 shows an example of a method for synthesizing Sym-HT-PcH, which is a preferable example of the material of the hole transport layer, and is not limited thereto, and may be synthesized using another method as appropriate. Can be.

  The phthalocyanine skeleton of the hole transport layer material according to this embodiment can be formed by a cyclization reaction of phthalonitrile by heating phthalonitrile and a metal salt coordinated as a central metal. Regarding the introduction of substituents, the hole transport layer material according to the present embodiment in which the substituents are introduced symmetrically can be easily synthesized by introducing the desired substituents into phthalonitrile in advance.

  In the synthesis, a hole transport layer material having various substituents can be provided by appropriately changing the type of the substituent introduced into phthalonitrile. Further, by appropriately changing the kind of the metal salt used for the cyclization reaction, it is possible to provide a hole transport layer material having various central metals. Thereby, the electrical characteristics of the hole transport layer material can be controlled, and it is possible to construct a hole transport layer material having higher performance. Therefore, it can be expected that a compound having a further improved hole transport property or a compound which does not require addition of any dopant as a hole transport layer material can be expected.

[Characteristics of hole transport layer material according to present embodiment]
The hole transport layer material according to the present embodiment has an excellent hole transporting property capable of stably and efficiently capturing and moving holes. The phthalocyanine constituting the skeleton of the hole transport layer material according to this embodiment is a condensed polyaromatic compound in which four isoindoles are crosslinked via a nitrogen atom. It is a ring-shaped structure with high planarity and forms a ring-like continuous π electron cloud. The π-electron clouds overlap between the phthalocyanine molecules and are stabilized in an arrangement in which a plurality of flat plates are stacked (referred to as “π-π stacking”). The holes can be moved in the direction in which the flat plates are stacked, and good hole transportability can be exhibited.

  The hole transport layer material according to the present embodiment also has excellent characteristics in terms of long-term durability. Phthalocyanines have been used in pigments and coatings and signs because they are not only sharp in color but also extremely chemically and physically stable and weather resistant. The above-mentioned π-π stacking state in phthalocyanine is extremely stable and strong, and external oxidation (emission of electrons) and reduction (injection of electrons) can be diffused by multiple molecules, As a stable state, and has high weather resistance. Since the hole transport layer material according to the present embodiment has such a phthalocyanine skeleton having weather resistance, it has a characteristic of high durability without being decomposed by light irradiation or temperature and humidity.

  In addition, when immobilized on a substrate such as laminating a conventional Spiro-OMeTAD as a hole transport layer, there is a problem that a gap is generated between molecules due to its molecular structure and other molecules are mixed. Specifically, the spiro ring structure at the molecular center of Spiro-OMeTAD is a five-membered ring structure, and the molecule takes a twisted structure of about 90%. As a result, the molecular structure becomes bulky, and the solvent molecules intrude into the intermolecular gaps to interrupt the hole transport, and the cobalt complex added as a dopant may drop off, etc., thereby stably and continuously exhibiting the hole transportability. I couldn't do that. However, since the hole transport layer material according to the present embodiment has high planarity as described above, no void is generated between molecules, electrical connection between molecules can be secured, and the hole transport property is reduced. It is possible to prevent problems such as mixing of other molecules that may be a factor causing the mixture between the molecules. This makes it possible to stabilize the hole transport performance and exhibit excellent performance in terms of durability.

  The hole transport layer material according to the present embodiment also has excellent characteristics in terms of solubility in a solvent. Phthalocyanine has a very low solubility in not only water but also an organic solvent due to strong interaction between molecules due to the above-mentioned π-π stacking, and its use has been limited. The hole transport layer material according to the present embodiment was so bulky that the π-π stacking was not hindered on the outer periphery of the phthalocyanine skeleton, and a substituent was uniformly introduced in order to improve solubility in a solvent. Thereby, the hole transport layer material according to the present embodiment becomes soluble in a solvent such as chlorobenzene, and the hole transport layer 5 of the hybrid solar cell 10 can be formed by a coating method such as spin coating. The compound having a spiro ring structure such as Spiro-OMeTAD, which has been widely used as the hole transport layer 5 of the solar cell 10 in the related art, can be used, and the manufacturing procedure can be similarly performed.

  Further, the hole transporting layer material according to the present embodiment controls the electrical properties such as the hole transporting property and the solubility in a solvent by changing the substituent and the central metal introduced to the outer periphery of the phthalocyanine skeleton. be able to. Thereby, it is possible to provide a hole transport layer material having higher performance. It is possible to more appropriately control the securing of the electrical connection between the molecules, and it can be expected to provide a compound with further improved hole transportability and a compound that does not require the addition of any dopant.

  The material of the hole transport layer according to the present embodiment can be synthesized easily and at low cost. The phthalocyanine skeleton can be formed by cyclizing phthalonitrile by heating phthalonitrile and a metal salt to be coordinated as a central metal. Regarding the introduction of a substituent, it is extremely easy to introduce a substituent symmetrically into phthalocyanine by introducing a desired substituent into phthalonitrile in advance. It can be provided at low cost. As described above, the hole transport layer material according to the present embodiment can be synthesized in a smaller number of steps and can be easily purified, as compared with a compound having a spiro ring structure such as a conventional Spiro-OMeTAD. The cost required for the synthesis can be reduced.

  As described above, the hole transport layer material according to this embodiment has excellent characteristics, and thus can be suitably used as the hole transport layer material of the solar cell 10.

[Characteristics of solar cell 10 according to present embodiment]
The solar cell 10 according to the present embodiment includes the hole transport layer 5 formed using the hole transport layer material of the present invention having excellent characteristics as described above. Specifically, since the hole transporting layer material according to the present embodiment has an excellent hole transporting property capable of capturing and moving holes stably and efficiently, the solar cell 10 according to the present invention can be used. By using this as the hole transport layer 5, the photoelectric conversion efficiency is improved, and the battery performance is improved.

  Further, since the composition of the hole transport layer material of this embodiment is stable, it can be expected that the same performance is always obtained. When using a conventional Spiro-OMeTAD with a hole transport layer material, it is necessary to add a dopant having a function of improving hole transport efficiency. On the other hand, the hole transport layer material of the present embodiment may be able to achieve good hole transport properties without adding a dopant.

  Since the hole transport layer material according to the present embodiment is also excellent in durability, the solar cell 10 according to the present embodiment uses the solar cell 10 as the hole transport layer 5 for long-term durability of the solar cell 10. Performance can be improved. Furthermore, in the conventional perovskite solar cell using Spiro-OMeTAD as the hole transport layer material, performance degradation of the perovskite crystal due to moisture absorption was a problem, but the perovskite crystal according to the present embodiment has weather resistance. Since the solar cell is covered with the hole transport layer material, the long-term durability of the solar cell can be improved from such a side.

  With the hole transport layer 5 formed of the hole transport layer material according to the present embodiment having such excellent characteristics, the battery performance of the solar cell 10 according to the present embodiment can be improved.

  Further, as described above, since the hole transport layer material according to the present embodiment can be synthesized at a low cost in a small number of steps, the cost of the solar cell 10 itself according to the present embodiment as the hole transport layer 5 is reduced. Can be achieved.

[Other Embodiments]
In the above-described embodiment, a hybrid type solar cell has been described as an example of the solar cell 10 using the hole transport layer material. It may be used for devices and the like.

  The present invention will be described in detail with reference to the following examples. In the following examples, “Sym-HT-PcH” is exemplified as the material of the hole transport layer, but the present invention is not limited to this.

(Example 1) Synthesis of hole transport layer material Hereinafter, as Example 1, a synthesis example of a hole transport layer material will be described. However, it is not limited to this embodiment.

  In this example, the synthesized hole transport layer material is referred to as “Sym-HT-PcH” shown in the general formula (IV). The synthesis scheme will be described with reference to FIG.

Synthesis of Sym-HT-PcH (Step 1) Synthesis of 4-iodophthalonitrile (Compound 2) Sulfuric acid (H ₂ SO ₄ , 12 mL) and water (6 mL) were mixed, and 4- Aminophthalonitrile (Compound 1: 2.5 g, 17.48 mmol) was added, stirred, and cooled to -10 ° C. To this reaction mixture, while maintaining the reaction mixture temperature at -10 to 0 ° C., sodium nitrite dissolved in water _{(NaNO 2: 1.206 g, 17.487} mmol) was added dropwise with stirring. After completion of the dropwise addition, the reaction mixture was quickly filtered using a suction filtration device, and the filtrate was separated. Sodium iodide (7.9 g, 47 mmol) was dissolved in 20 ml of water, the cooled filtrate was added dropwise to the cooled one, and the mixture was kept stirring at 0 ° C. When the temperature of the mixture that turned black was raised to room temperature with stirring, black precipitates appeared, and the solid matter was separated by filtration. This solid was dissolved in dichloromethane (CH ₂ Cl ₂ : 50 mL), washed twice with 50 ml of cold water, washed with 50 ml of a 10% sodium hydrogen carbonate (NaHCO ₃ ) solution, and once again with 50 ml of cold water and saturated sodium sulfite. It was washed once with 50 ml of an aqueous solution of (Na ₂ S ₂ O ₃ ) and finally three times with 50 ml of water. After the washed solution was dried over magnesium sulfate (MgSO ₄ ), the solvent was distilled off until the total amount became about 10 ml. The residue was purified by chromatography using a silica gel column to obtain a target white solid of 4-iodophthalonitrile (compound 2) in a yield of 70%.

(Step 2) Synthesis of 4- (5-hexylthiophen-2-yl) phthalonitrile (compound 4) 4- (5-hexylthiophen-2-yl) phthalonitrile: 4-iodophthalonitrile synthesized in Step 1 described above. (Compound 2: 2.5 g, 9.84 mmol) and 2- (5-hexylthiophen-2-yl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2- (5-hexylthiophen- 2-yl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane, compound 3: 3.183 g, 10.82 mmol) was dissolved in THF (100 mL), then water (20 mL) and sodium carbonate ( Sodium bicarbonate: 17.36 g, 206.6 mmol) was added. After degassing with an argon gas for 30 minutes, a palladium catalyst ([Pd (PPh ₃ ) ₄ ]: 1.13 g, 0.984 mmol) was added, and the mixture was heated and refluxed for 12 hours under an argon stream. After evaporating the solvent, the residue was purified by chromatography on a column packed with silica gel to obtain 2.3 g of the desired 4- (5-hexylthiophen-2-yl) phthalonitrile (compound 4) in a yield of 86.9%. Was.

(Step 3) Synthesis of Sym-HT-PcH (general formula IV) 4- (5-hexylthiophen-2-yl) phthalonitrile (compound 4: 2.00 g, 6.80 mmol) synthesized in step 1 described above and Zn ( OAc) ₂ 2H ₂ O (594 mg, 2.72 mmol) was dissolved in 20 mL of pentanol. When this was heated to 100 ° C., a catalytic amount of diazabicycloundecene (DBU) was added, and the mixture was refluxed for 24 hours. After the completion of the reaction, the solvent was distilled off, and the residue was purified by chromatography using a column packed with silica gel to obtain 0.6 g of the final target product, Sym-HT-PcH (general formula IV), at a yield of 23%. I got it.

(Example 2) Production of solar cell 10 Hereinafter, as Example 2, a production example of the solar cell 10 will be described. However, it is not limited to this embodiment.

First, a glass substrate with a transparent conductive film (substrate 2) formed by forming a 20 mm × 20 mm × 2 mm transparent substrate 21 on a transparent glass plate and a fluorine-doped tin oxide (FTO) as a transparent conductive film by CVD is prepared. Then, a concave portion 221 from which FTO was removed was formed, and sufficiently washed. Next, a dense layer (thickness: 20 nm) of titanium dioxide (TiO ₂ ) serving as a blocking layer 3 was formed on the entire surface of the glass substrate with a transparent conductive film by ALD (atomic layer deposition).

A solution obtained by diluting a commercially available TiO ₂ nanoparticle paste four-fold with ethanol was dropped on the masking blocking layer 3, applied by spin coating, and dried at 80 ° C. After drying, the masking was removed, and sintering was performed at 500 ° C. for 15 minutes to form a TiO ₂ nanoparticle layer to be a porous semiconductor 41 having a thickness of 500 nm. Further, this was immersed in a titanium tetrachloride aqueous solution (400 mmol / l) at 70 ° C. for 30 minutes, rinsed with pure water, and sintered at 500 ° C. for 30 minutes. After sintering, it was allowed to cool to room temperature.

Next, an N, N-dimethylformamide solution 42 (1.2 mol / l) of lead iodide (PbI ₂ ) is prepared and dropped, and lead iodide is introduced into the layer composed of the porous semiconductor 41 by spin coating. After infiltration and removal of excess solution, the mixture was dried at 80 ° C. for 30 minutes.

Next, a porous semiconductor 41 containing the substrate 2, the blocking layer 3, and the lead dioxide was placed in an 8 mg / ml methyl ammonium iodide (CH ₃ NH ₃ I, sometimes referred to as “MAI”) isopropyl alcohol solution 43. After immersion at room temperature for 15 minutes, the mixture was irrigated with a pure isopropyl alcohol solution, spin-coated, dried at 100 ° C. for 15 minutes, and rapidly cooled to room temperature. As a result, a crystal of the perovskite dye [(CH ₃ NH ₃ ) PbI ₃ ] as the dye 44 was generated.

  Next, a chlorobenzene solution of Sym-HT-PcH or Spiro-OMeTAD which is a hole transport layer material (FK209 (Tris (2- (1H-pyrazol-1-yl) -4-tert-butylpyridine) cobalt ( III) Tris (bis (trifluoromethylsulfonyl) imide etc. added to both) 72.3mg / ml 40μl was added dropwise, the excess solution was removed by spin coating, and dried to form a 500nm thick hole on the power generation layer 4. A transport layer 5 was formed, and finally, a gold film was formed by a vacuum evaporation method on the surface of the laminated body 11 on which these layers were laminated, and an electrode 6 having a thickness of 100 nm including a photoelectrode 61 and a counter electrode 62 was laminated. .

(Example 3) Performance evaluation of solar cell Hereinafter, as Example 3, performance evaluation of the solar cell 10 was performed.

9 and 10 are graphs showing the average battery performance of Sym-HT-PcH or Spiro-OMeTAD. FIG. 9 shows Sym-HT-PcH and FIG. 10 shows Spiro-OMeTAD. 9 and 10 show an open circuit voltage (Voc) -short-circuit current (Isc) characteristic representing battery performance. The open voltage Voc is a voltage when no current flows through the solar cell 10, and the short-circuit current Isc is a current when the voltage is 0V. Jsc in the figure is a short-circuit current density (mA / cm ² ) obtained by dividing the short-circuit current Isc by the effective light receiving area.

ここで、形状因子FF（フィルファクター）とは、電流と電圧の積が最大となる点における最大出力Pmaxを（Voc×Jsc）で割って得られる曲線因子であり、PCEは、（Voc×Jsc×FF÷入射光強度）で計算される。 Table 1 shows the battery performance of the solar cell 10 quantified.

Here, the form factor FF (fill factor) is a fill factor obtained by dividing the maximum output Pmax at the point where the product of current and voltage is maximum by (Voc × Jsc), and PCE is (Voc × Jsc × FF ÷ incident light intensity).

  As can be understood from FIGS. 9 and 10 and Table 1, the cell performance of the solar cell using Sym-HT-PcH as the hole transport layer is about 70 to 80% of the solar cell using Spiro-OMeTAD. Was. At present, using Spiro-OMeTAD as the hole transport layer material shows higher performance, but this experiment on Sym-HT-PcH is an initial experiment. Therefore, the battery performance at the stage where conditions such as solution concentration and the like for optimizing the solar cell as a hole transport layer are not set. Other than compounds having a spiro ring structure, such as Spiro-OMeTAD, none of them showed as high performance as Sym-HT-PcH in the initial experiments. Further, further improvement in performance can be expected by optimizing the solution concentration, optimizing the substituents, and the like. From this, it can be expected that the use of a phthalocyanine derivative such as Sym-HT-PcH as the hole transport layer material will greatly improve the photoelectric conversion efficiency of the solar cell.

(Example 4) Durability evaluation of solar cell Hereinafter, as Example 4, the durability of the solar cell 10 was evaluated.

  The cells of the solar cell 10 manufactured in Example 2 were stored in a dark place in air at a temperature of 23 ° C. and a humidity of 20%, and the cell efficiency was measured periodically. At this time, the cells of the solar cell 10 were exposed to the air without being covered with a capsule or the like. The results are shown in the graph of FIG. FIG. 11 shows the change over time (days) of the cell efficiency, in which the ratio of the change in the cell efficiency to the maximum performance value of the cell of each solar cell 10 when the maximum performance value is 1 is plotted.

  From FIG. 11, the highest performance was recorded in the Sym-HT-PcH cell two days later than immediately after the production. In the Spiro-OMeTAD cell, the highest value was recorded immediately after fabrication, and the performance gradually decreased thereafter. After 9 days, Sym-HT-PcH had a maximum value of 78%, and Spiro-OMeTAD had 58%, indicating that the cell using Sym-HT-PcH has higher durability.

  INDUSTRIAL APPLICABILITY The present invention can be used as a hole transport layer material used for a hybrid solar cell including a perovskite dye formed of an organic and inorganic hybrid compound.

2 Substrate 3 Blocking layer 4 Power generation layer 5 Hole transport layer 6 Electrode 10 Solar cell 11 Stack 21 Transparent substrate 22 Transparent conductive film 41 Porous semiconductor 44 Dye 61 Photo electrode 62 Counter electrode

Claims (4)

A hole transport layer material which is a compound represented by the following general formula (I).

(In the general formula (I),
M is zinc (Zn ) ,
R ^1b , R ^2a , R ^3a and R ^4b are the following substituents (A),
R ^1a , R ^2b , R ^3b , and R ^4a are hydrogen atoms,
The substituents selected for R ^1b , R ^2a , R ^3a and R ^4b are the same.

Here, the the X ¹ substituent (A), C ₆ ~C Ru ₈ alkyl der. ) In the compound represented by the general formula (I),
The substituent (A) is 5-hexenyl - thiophen-2-yl group, or 5- (2-ethylhexyl) - thiophen-2-yl Ru groups der, hole transport layer material according to claim 1. The hole transport layer material according to claim 1, wherein the compound is represented by the following general formula (IV).

A substrate having a transparent conductive film,
A blocking layer for transferring electrons to the transparent conductive film and preventing reverse electron transfer,
A power generation layer formed by adsorbing a dye that generates the electrons by being excited by light to a porous semiconductor,
Holes generated from the dye pass through, a hole transport layer having the hole transport layer material, a laminated body laminated in order,
Photoelectrode releasing the electrons through the transparent conductive film, and, any one of claim 1 to 3, and a, and electrodes constituted by opposing electrodes provided on the surface of the hole transport layer A solar cell using the hole transport layer material described in 1.

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