JP2016119468A - Organic inorganic hybrid solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic inorganic hybrid solar cell low in leakage current, excellent in photoelectric conversion efficiency, and suppressed in photo-deterioration.SOLUTION: A solar cell 1 shown in (a) is a laminate and comprises a substrate 2, an electrode 3, a thin film layer 4, an organic inorganic hybrid semiconductor layer 6, a hole transport layer 7 and a counter electrode 8, and a solar cell 1 shown in (b) is a composite film, the organic inorganic hybrid semiconductor layer 6 entering a clearance of a porous layer 5 and forming a composite body with the porous layer 5. The electrode 3 has an arithmetic average roughness Ra of 25 nm or less, and the organic inorganic hybrid semiconductor layer 6 has a perovskite structure represented by general formula R-M-X(where, R represents an organic molecule, M represents a metal atom, and X represents a halogen atom or a chalcogen atom).SELECTED DRAWING: Figure 1

Description

The present invention relates to an organic-inorganic hybrid solar cell with little leakage current, excellent photoelectric conversion efficiency, and suppressed photodegradation.

In recent years, a transparent electrode has been developed as an indispensable constituent member in producing various displays such as liquid crystal, plasma, and organic electroluminescence (organic EL). In addition to the above, the transparent electrode substrate is also an indispensable element in various solar cells. A transparent electrode substrate for use in solar cells is required to have low resistance and high light transmittance as required physical properties.

Conventionally, as transparent electrodes, metal thin films such as Au, Ag, Pt, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), fluorine-doped oxidation Metal oxide thin films such as tin (FTO) and antimony-doped tin oxide (ATO), conductive nitride thin films such as TiN, ZrN, and HfN, and conductive boride thin films such as LaB ₆ are used. As a transparent electrode for solar cell applications, it is necessary to achieve both low resistivity and high light transmittance as described above. However, it is difficult to achieve both of them in a metal thin film, and a metal oxide thin film has the best characteristics. Therefore, it has become the mainstream of transparent electrodes.

On the other hand, in a solar cell, a photoelectric conversion element is formed by sandwiching at least one of a photoelectric conversion layer, which is a stacked body of an N-type semiconductor layer and a P-type semiconductor layer, with two electrodes using the transparent electrode. . In addition, as a photoelectric conversion layer, use of a composite film obtained by mixing and compounding an N-type semiconductor and a P-type semiconductor instead of a stacked body has been studied. In such a photoelectric conversion element, photocarriers are generated by photoexcitation, and an electric field is generated by electrons moving through an N-type semiconductor and holes moving through a P-type semiconductor.

Many of the photoelectric conversion elements currently in practical use are inorganic solar cells using an inorganic semiconductor such as silicon. However, the range of use is limited because of high manufacturing cost, large size, and rigid size. Therefore, attention is focused on organic solar cells using organic semiconductors as described in Patent Document 1, but photoelectric conversion efficiency is inferior to that of inorganic solar cells.

Therefore, in recent years, a photoelectric conversion material having a perovskite structure using lead, tin or the like as a central metal, which is called an organic-inorganic hybrid semiconductor as described in Patent Document 2 or Non-Patent Document 1, has been discovered.

JP 2006-344794 A JP 2014-72327 A

M.M. M.M. Lee, et al, Science, 2012, 338, 643

However, since the leakage current exists in the organic-inorganic hybrid solar cell described in Patent Document 2 or Non-Patent Document 1, further efficiency improvement is expected by suppressing the leakage current. In addition, the organic-inorganic hybrid solar cell described in Patent Document 2 or Non-Patent Document 1 has been confirmed to exhibit a phenomenon in which performance deteriorates when light is continuously applied (light degradation). Therefore, an object of the present invention is to provide an organic-inorganic hybrid solar cell that has little leakage current, is excellent in photoelectric conversion efficiency, and is suppressed from photodegradation.

The present invention relates to a substrate having an electrode having an arithmetic average roughness Ra of 25 nm or less, an electron transport layer, a general formula R-M-X ₃ (provided that R is measured according to JIS B 0601-2001). Is an organic molecule, M is a metal atom, X is a halogen atom or a chalcogen atom.) And an organic-inorganic hybrid semiconductor layer having a perovskite structure.
The present invention is described in detail below.

As a result of intensive studies on the cause of the photocurrent deterioration due to the increase of the leakage current value, the present inventors speculated that the cause was the surface roughness of the electrode surface of the substrate having the electrodes. Due to the large surface roughness of the electrode, the film-forming property of the semiconductor layer laminated on the electrode is reduced, and the leakage current is generated when the counter electrode etc. is in direct contact with the electrode due to the formation of cracks, pinholes, etc. It seems to be. That is, the present inventors can suppress the leakage current and improve the photoelectric conversion efficiency by setting the arithmetic average roughness Ra measured in accordance with JIS B 0601-2001 of the electrode to 25 nm or less. Furthermore, it discovered that light deterioration could be suppressed and came to complete this invention.
In addition, suppression of leakage current and suppression of photodegradation by setting the arithmetic average roughness Ra of the electrode to 25 nm or less are noticeable when an organic-inorganic hybrid semiconductor layer having a perovskite structure with high charge separation ability is used. For example, in the case of using an inorganic semiconductor layer, even if the arithmetic average roughness Ra of the electrode is set to 25 nm or less, no significant leakage current suppression or light degradation suppression is observed.

The battery characteristics of a solar cell can be generally expressed by a product of three factors of a short circuit current density, an open circuit voltage, and a fill factor (FF). Among them, FF indicates the recovery efficiency of the generated carrier, and the resistance value at the interface of the bulk or each semiconductor layer is low, and when the leakage current is small, the FF shows a high value, resulting in the photoelectric conversion efficiency. Will improve.

The organic-inorganic hybrid solar cell of the present invention has a substrate having electrodes.
The electrode has an arithmetic average roughness Ra measured in accordance with JIS B 0601-2001 of 25 nm or less. The lower limit of the arithmetic average roughness Ra is not particularly limited, and may be 1 nm or more. On the electrode, semiconductor layers are stacked in multiple layers, but by suppressing the arithmetic average roughness Ra to 25 nm or less, the film formability of each layer is improved, cracks, pinholes, etc. can be suppressed, Leakage current can be suppressed. The arithmetic average roughness Ra is preferably 20 nm or less, and more preferably 15 nm or less.
The arithmetic average roughness Ra can be measured using a Dimension FastScan AFM Scanist Air mode manufactured by Bruker.

Examples of the electrode include a transparent electrode and a metal electrode.
The above transparent electrode ITO, IZO, AZO, GZO, FTO, metal oxide thin film of ATO, etc., TiN, ZrN, conductive nitride film such as HfN, include conductive boride thin film such as LaB _6. Of these, ITO, IZO, AZO, GZO, FTO, or ATO are preferable from the viewpoint of low resistance and high light transmittance, and a semiconductor layer laminated on the transparent electrode when manufacturing an organic-inorganic hybrid solar cell. FTO or ATO having high heat resistance is more preferable because of heat treatment.

When the electrode is a transparent electrode, the substrate is not particularly limited, and examples thereof include a transparent glass substrate such as soda lime glass and non-alkali glass, a ceramic substrate, and a transparent plastic substrate.

It has been found that the arithmetic average roughness Ra measured in accordance with JIS B 0601-2001 of the transparent electrode varies depending on the type of electrode or the production method. Examples of the production method of the transparent electrode include a sputtering method. And dry process methods such as sol-gel method, spray pyrolysis deposition method and the like. In the spray pyrolysis deposition method, the arithmetic average roughness Ra of the transparent electrode can be easily adjusted by adjusting the spray amount, spray speed, substrate temperature, and the like.

When the electrode is a metal electrode, the material of the metal electrode is not particularly limited, and examples thereof include titanium, aluminum, SUS, and copper. Of these, titanium is preferable from the viewpoint of excellent suppression of light degradation. The reason why titanium suppresses photodegradation is unclear, but it is thought that a titanium oxide layer is formed at the interface between the titanium electrode and the electron transport layer, and the titanium oxide improves the density of the electron transport layer. The metal electrode may be a thin film of the metal electrode material, or may be a laminate of the metal electrode material on a substrate by sputtering, vapor deposition, or the like.

Although it does not specifically limit as said board | substrate in case the said electrode is a metal electrode, Transparent glass substrates, such as soda-lime glass and an alkali free glass, a ceramic substrate, a transparent plastic substrate, a metal thin film, etc. are mentioned. When the metal thin film is used as the substrate, the metal thin film may be the same material as the metal electrode or a different material. When a metal thin film is used as the substrate, the arithmetic average roughness Ra of the electrode can be adjusted according to the type of the metal thin film. The preferable lower limit of the thickness of the metal thin film is 1 μm, and the preferable upper limit is 500 μm.

When the metal thin film is used as a substrate, it is preferable to laminate an insulating material on the metal thin film and further laminate an electrode.
By setting it as said structure, the performance of an organic inorganic hybrid solar cell can be improved. The insulating material is not particularly limited as long as it is an insulating material, and examples thereof include an inorganic insulating film and an insulating resin. Examples of the inorganic insulating film include SiO2 and Al2O3, and examples of the insulating resin include polyimide resin, silicone resin, and acrylic resin. Especially, it is preferable that the said insulating material is an insulating resin from a viewpoint which adjusts arithmetic mean roughness Ra of an electrode below the said upper limit easily. In particular, polyimide resin and silicone resin are more preferable because of excellent heat resistance and mechanical strength. The insulating material preferably has a lower limit of 500 nm and an upper limit of 50 μm.

When the metal thin film is used as the substrate, the metal thin film may be used as the substrate having the electrodes as it is. By using the metal thin film as it is as a substrate having an electrode, the obtained thin film solar cell can be a flexible solar cell. In addition, when a metal thin film is used as a board | substrate which has an electrode, the arithmetic mean roughness of the metal thin film surface is equivalent to the arithmetic mean roughness of the said electrode.

The preferable lower limit of the film thickness of the electrode is 10 nm, and the preferable upper limit is 1000 nm. By setting the thickness of the electrode within the above range, sufficient performance as an electrode can be exhibited, and a decrease in photoelectric conversion efficiency (photodegradation) due to continued irradiation with light can be reliably suppressed.

In addition to the substrate having the above electrode, the organic-inorganic hybrid solar cell of the present invention has an electron transport layer, a general formula R-M-X ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or An organic-inorganic hybrid semiconductor layer having a perovskite structure represented by a chalcogen atom). The electron transport layer and the organic / inorganic hybrid semiconductor layer are preferably in contact with each other, and the electrode, the electron transport layer, and the organic / inorganic hybrid semiconductor layer are preferably arranged in this order. The electron transport layer is preferably provided between the electrode and the organic-inorganic hybrid semiconductor layer. In such an organic-inorganic hybrid solar cell, photocarriers (electron-hole pairs) are generated in the organic-inorganic hybrid semiconductor layer by photoexcitation, and an electric field is generated by the movement of the photocarriers in the semiconductor.
The organic / inorganic hybrid solar cell of the present invention only needs to contain the organic / inorganic hybrid semiconductor layer and the electron transport layer as a photoelectric conversion layer, and the electron transport layer and the organic / inorganic hybrid semiconductor layer are stacked. Or a composite film in which the electron transport layer and the organic-inorganic hybrid semiconductor layer are combined, but the charge separation efficiency of the organic-inorganic hybrid semiconductor layer can be improved. A composite membrane is preferred. The laminated body has a structure as shown in FIG. 1A, in which each layer is connected in a thin film shape. The composite film is a state in which the layers are mixed as shown in FIG. 1B described later. A membrane.

The electron transport layer is preferably stacked on the electrode, and the material of the electron transport layer is preferably an oxide semiconductor. The oxide semiconductor is not particularly limited, but an oxide of titanium, aluminum, zinc, niobium, silicon, tantalum, or tin is preferable. These materials may be used alone or in combination of two or more. The electron transport layer has a function of transporting generated electrons to the electrode, such as titanium oxide.

The electron transport layer preferably has at least a two-layer structure. The first layer disposed on the electrode side is preferably a layer having high followability to the lower layer and good film forming properties (this layer is hereinafter referred to as a thin film layer). High followability is a state in which a film that does not have cracks, pinholes, or the like and is difficult to expose the lower layer is formed by forming the film according to the shape of the lower layer. By providing the thin film layer on the electrode side, the organic / inorganic hybrid semiconductor layer and the hole transport layer above the electron transport layer, and further, the counter electrode is prevented from coming into direct contact with the electrode, and leakage current is reduced. Can be suppressed.

The method for forming the thin film layer is not particularly limited, and examples thereof include a method for forming an alkoxide solution or a complex solution of each element by a spray pyrolysis method or a spin coating method.

The second layer of the electron transport layer is preferably a porous layer. That is, it is preferable that the electron transport layer includes the thin film layer and the porous layer, and the thin film layer is disposed on the electrode side.
The average diameter of the pores of the porous layer is preferably 5 to 100 nm. When the electron transport layer contains the porous layer, the organic-inorganic hybrid semiconductor layer and the hole transport layer can penetrate (enter) into the pores of the porous layer, and the surface area of each interface increases. , The amount of charge generated can be increased. When the average diameter of the pores is 5 nm or more, a sufficient interface area is ensured, and the amount of generated charges increases. When the average diameter of the pores is 100 nm or less, the amount of generated charges increases due to the reason that the organic-inorganic hybrid semiconductor layer and the hole transport layer are sufficiently easily penetrated into the pores of the porous layer. The more preferable lower limit of the average diameter of the pores is 8 nm, the more preferable upper limit is 70 nm, the still more preferable lower limit is 12 nm, and the still more preferable upper limit is 50 nm.
In addition, the pores herein are structures that are not isolated in the porous layer but are three-dimensionally connected to the film surface. The average diameter of the pores can be measured by a gas adsorption method or the like.

The method for forming the porous layer is not particularly limited, and examples thereof include a spin coating method, a screen printing method, a spray pyrolysis method, and an aerosol deposition method.

One example of the method for forming the porous layer is a screen printing method. The screen printing method is a method in which a dispersion liquid in which particles made of an electron transport material are dispersed in an organic solvent is printed on a lower layer, and the organic solvent is volatilized to form a porous layer.
When the porous layer is formed by such a screen printing method, the dispersion may contain an organic binder. In that case, after the dispersion liquid (paste) containing the particle | grains which consist of the said electron transport material, the said organic binder, and the said organic solvent is printed on a lower layer, the said organic solvent is volatilized, and also the above-mentioned by high temperature baking processing. It is necessary to eliminate the organic binder.
The organic binder is not particularly limited, but it is preferable to use ethyl cellulose or (meth) acrylic resin. A (meth) acrylic resin is particularly preferred because it is excellent in low-temperature decomposability and can be made into a paste with a small amount of organic residue even when performing low-temperature firing.

The (meth) acrylic resin is not particularly limited as long as it decomposes at a low temperature of about 300 ° C., and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n-butyl (meth) ) Acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobornyl (meth) acrylate, n-stearyl (meth) acrylate, benzyl (meth) acrylate In addition, a polymer obtained by polymerizing at least one selected from the group consisting of (meth) acrylic monomers having a polyoxyalkylene structure is suitably used. Here, for example, (meth) acrylate means acrylate or methacrylate. Among them, polyisobutyl methacrylate, which is a polymer of isobutyl methacrylate having a high glass transition temperature (Tg) and excellent low-temperature degreasing property, is preferable because a high viscosity can be obtained with a small amount of resin. Moreover, the average diameter of the pores of the porous layer can be adjusted by changing the type or addition amount of the organic binder in addition to changing the particle diameter of the particles made of the electron transport material.

The electron transport layer is preferably heated and fired in order to improve crystallinity and necking. The preferable lower limit of the firing temperature is 100 ° C., the preferable upper limit is 600 ° C., the more preferable lower limit is 150 ° C., and the more preferable upper limit is 500 ° C. Moreover, the same effect as heat-firing can be obtained by irradiating the electron transport layer with active energy rays. The amount of organic residue can be further reduced by irradiating with active energy rays after the heating and baking.

Examples of the active energy rays include ultraviolet rays, plasma, and electron beams.
In the case of irradiating the ultraviolet rays, it is preferable to irradiate the ultraviolet rays so that the integrated light amount becomes 100 J / cm ² or more. If the integrated light quantity is less than 100 J / cm ² , organic residues may not be sufficiently removed. A more preferred lower limit of the cumulative light quantity is 150 J / cm ^2, preferable upper limit is 10000 J / cm ^2. The integrated light quantity can be simply calculated by irradiation intensity (mW / cm ² ) × irradiation time (seconds).

Moreover, it is preferable that the irradiation intensity of an ultraviolet-ray is 0.5-1000 mW / cm < ² >. Furthermore, the irradiation time of ultraviolet rays is preferably 1 second to 300 minutes, more preferably 1 second to 60 minutes. If the irradiation intensity is too low or the irradiation time is too short, the removal of the organic residue will only partially proceed, so that a sufficient effect cannot be obtained, the irradiation intensity is too high, or the irradiation time is too long. Then, ultraviolet deterioration or thermal deterioration of the substrate having the electrode may be exerted.

The method of irradiating the active energy ray is not particularly limited, and for example, a method of irradiating ultraviolet rays using a low-pressure mercury lamp, a high-pressure mercury lamp, a mercury-xenon lamp, or the like, or irradiating plasma using a plasma generator or the like. Methods and the like.

When irradiating the active energy ray, it is preferable to irradiate the active energy ray from both the front side (the side opposite to the substrate having the electrode) and the back side (the substrate side having the electrode) of the electron transport layer. Thereby, active energy rays can be sufficiently irradiated to the inside of the electron transport layer. As a result, even with a small amount of integrated light, the effect of active energy ray irradiation can be obtained sufficiently, leading to a reduction in the time of the entire manufacturing process. Note that the irradiation from the front side and the irradiation from the back side may be performed simultaneously, or may be performed sequentially in a plurality of times.

After irradiating the electron transport layer with active energy rays, it is preferable to further irradiate the electron transport layer with pulsed white light having a small pulse width. By irradiating the pulsed white light, densification due to melting of the surface between the particles made of the electron transport material occurs, and as a result, the surface resistance can be reduced.

The pulse white light preferably has a pulse width of 0.1 to 10 ms. Thereby, powerful light energy can be irradiated instantaneously.

The cumulative amount of the pulsed white light is not particularly limited, but is preferably 4 J / cm ² or more, and more preferably 15 to 40 J / cm ² . Thereby, sufficient energy can be applied to the melting of the surface between the particles made of the electron transport material. The number of times of irradiation with the pulsed white light is preferably 1 to 5 times.

The method of irradiating the pulsed white light is not particularly limited, and examples thereof include a method using a halogen flash lamp, a xenon flash lamp, an LED flash lamp and the like, and a method using a xenon flash lamp is particularly preferable.

The organic-inorganic hybrid semiconductor layer has a perovskite structure represented by the general formula R-M-X ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). is there. An example of the crystal structure (perovskite structure) of the organic-inorganic hybrid semiconductor layer is schematically shown in FIG. Although details are not clear, by having the perovskite structure, since the orientation of the octahedron in the crystal lattice can be easily changed, the mobility of electrons in the organic-inorganic hybrid semiconductor layer is increased, It is estimated that high photoelectric conversion efficiency can be realized.

In the general formula R-M-X ₃ of the organic-inorganic hybrid semiconductor layer, R is preferably a molecule represented by C ₁ N _m H _n (l, m, and n are all positive integers). R is specifically methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine , Tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, Azole, imidazoline, carbazole, methylcarboxyamine, ethylcarboxyamine, propylcarboxyamine, butylcal Kishiamin, pentyl carboxyamine, hexyl carboxyamine, formamidinium, guanidine and their ions (e.g., such as ammonium (CH 3 _{NH 3)),} and phenethyl ammonium, and the like. Of these, methylamine, ethylamine, propylamine, propylcarboxyamine, butylcarboxyamine, pentylcarboxyamine, formamidinium, guanidine or their ions and phenethylammonium are preferred, and methylamine, ethylamine, pentylcarboxyamine, formamidinium are preferred. More preferred are guanidine or these ions.

Examples of M include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. Among these, lead and tin are preferable from the viewpoint of overlapping of electron orbits. These metal atoms may be used independently and 2 or more types may be used together.

X is a halogen atom or a chalcogen atom, and examples thereof include chlorine, bromine, iodine, and sulfur. These halogen atoms or chalcogen atoms may be used alone or in combination of two or more. Among them, by containing a halogen atom in the structure, the material constituting the organic-inorganic hybrid semiconductor layer is likely to be soluble in an organic solvent, and can be applied to an inexpensive printing method, etc. It preferably contains a halogen atom. Furthermore, since the energy band gap of the said organic-inorganic hybrid semiconductor layer becomes narrow, it is more preferable that iodine is included.

The organic-inorganic hybrid semiconductor layer is preferably a crystalline semiconductor. A crystalline semiconductor means a semiconductor capable of measuring an X-ray scattering intensity distribution and detecting a scattering peak. When the organic-inorganic hybrid semiconductor layer is a crystalline semiconductor, the mobility of electrons in the organic-inorganic hybrid semiconductor layer is increased, and the photoelectric conversion efficiency is improved.
In addition, the degree of crystallization can be evaluated as an index of crystallization. Crystallinity refers to the separation of the crystalline-derived scattering peak and the amorphous-derived halo detected by X-ray scattering intensity distribution measurement by fitting, and obtaining the respective intensity integrals to obtain the crystalline portion of the whole. Can be obtained by calculating the ratio. The preferred crystallinity of the organic-inorganic hybrid semiconductor layer is 30% or more. When the crystallinity is 30% or more, the mobility of electrons in the organic-inorganic hybrid semiconductor layer increases, and the photoelectric conversion efficiency increases. A more preferable crystallinity is 50% or more, and a further preferable crystallinity is 70% or more. Examples of a method for increasing the crystallinity of the organic-inorganic hybrid semiconductor layer include thermal annealing, irradiation with intense light such as laser, and plasma irradiation.

In the organic-inorganic hybrid solar cell of the present invention, it is more preferable to provide a hole transport layer in addition to the above layers. The hole transport layer is preferably provided between the organic-inorganic hybrid semiconductor layer and a counter electrode described later. The material of the hole transport layer is not particularly limited. Organic conductive materials having any of porphyrin skeleton, molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, copper oxide, tin oxide and other P-type metal oxides, molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide, etc. Surfactants such as P-type metal sulfide, fluoro group-containing phosphonic acid, and carbonyl group-containing phosphonic acid can be mentioned. Among these, an organic conductive material having any one of a spirobifluorene skeleton, a thiophene skeleton, a phthalocyanine skeleton, a naphthalocyanine skeleton, or a benzoporphyrin skeleton is preferable because it becomes a relatively durable P-type semiconductor. These organic conductive materials may be low molecules or polymers. The organic conductive material may contain a dopant such as lithium.

The organic-inorganic hybrid solar cell of the present invention preferably further has a counter electrode in addition to the above electrodes. The material of the counter electrode is not particularly limited, and conventionally known materials can be used. For example, metals such as gold, silver, and platinum, conductive materials such as CuI, ITO, SnO ₂ , FTO, AZO, IZO, and GZO Examples thereof include a transparent material and a conductive transparent polymer. Further, as the material of the counter electrode (anode), for _{example, CuI, ITO, SnO 2,} FTO, AZO, IZO, a conductive transparent material such as GZO, sodium, sodium - potassium alloy, lithium, magnesium, aluminum, magnesium - silver Examples thereof include a mixture, a magnesium-indium mixture, an aluminum-lithium alloy, an Al / Al ₂ O ₃ mixture, and an Al / LiF mixture. These materials may be used alone or in combination of two or more.

An example of the organic-inorganic hybrid solar cell of the present invention is schematically shown in FIG. The organic / inorganic hybrid solar cell 1 shown in FIG. 1 (a) is a laminated body, and includes a substrate 2, an electrode 3, a thin film layer 4, an organic / inorganic hybrid semiconductor layer 6, a hole transport layer 7, and a counter electrode 8. Among these, the preferable lower limit of the film thickness of the thin film layer 4 is 10 nm, and the preferable upper limit is 2 μm. The preferable lower limit of the film thickness of the organic-inorganic hybrid semiconductor layer 6 and the hole transport layer 7 is 10 nm, and the preferable upper limit is 1 μm.

Another example of the organic-inorganic hybrid solar cell of the present invention is schematically shown in FIG. The organic / inorganic hybrid solar cell 1 shown in FIG. 1B is a composite film, and includes a substrate 2, an electrode 3, a thin film layer 4, a porous layer 5, an organic / inorganic hybrid semiconductor layer 6, a hole transport layer 7, and a counter electrode 8. Among them, the organic-inorganic hybrid semiconductor layer 6 enters the gap between the porous layers 5 and forms a composite with the porous layer 5. The preferable lower limit of the film thickness of the layer including the porous layer 5 and the organic-inorganic hybrid semiconductor layer 6 is 50 nm, and the preferable upper limit is 5 μm. When the film thickness is 50 nm or more, photoelectric conversion efficiency is increased by sufficiently absorbing light. Further, when the thickness is 5 μm or less, the generated charges are easily collected efficiently by the electrode, and thus the photoelectric conversion efficiency is increased. The more preferable lower limit of the film thickness of the layer including the porous layer 5 and the organic-inorganic hybrid semiconductor layer 6 is 100 nm, and the more preferable upper limit is 2 μm.

An example of the organic-inorganic hybrid solar cell of the present invention when a metal thin film is used for the substrate is schematically shown in FIG. In the organic / inorganic hybrid solar cell of the present invention using a metal thin film as a substrate, a portion corresponding to the substrate 2 in FIG. 1 is a laminate of a metal thin film 9 and an insulating material layer 10, and an electrode 3 is further laminated thereon. ing. The layer above the electrode 3 may be a laminate as shown in FIG. 2A, or may be a composite film as shown in FIG.

FIG. 3 schematically shows an example of the organic-inorganic hybrid solar cell of the present invention when a metal thin film is used as it is as the substrate having the electrode. When the metal thin film is used as it is, the organic-inorganic hybrid solar cell of the present invention has a structure in which the electron transport layer (thin film layer 4) is directly laminated on the metal thin film 9. The layer above the thin film layer may be a laminate as shown in FIG. 2 (a) or a composite film as shown in FIG. 2 (b).

According to the present invention, it is possible to provide an organic-inorganic hybrid solar cell that has low leakage current, excellent photoelectric conversion efficiency, and suppressed photodegradation.

It is sectional drawing which shows typically an example of the laminated body (a) and composite film body (b) in the organic-inorganic hybrid solar cell of this invention. It is sectional drawing which shows typically an example of the laminated body (a) and composite film body (b) in the organic-inorganic hybrid solar cell of this invention which used the metal electrode for the electrode and the metal thin film for the board | substrate. It is sectional drawing which shows typically an example of the laminated body (a) and composite film body (b) in the organic-inorganic hybrid solar cell of this invention at the time of using a metal thin film as it is as a board | substrate which has an electrode. It is a schematic diagram which shows an example of the crystal structure (perovskite structure) of an organic inorganic hybrid semiconductor layer.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
On a glass substrate, an FTO film having a thickness of 1000 nm is formed as a cathode by a spray pyrolysis deposition method so as to have an arithmetic average roughness Ra = 8.8 nm, and pure water, acetone, and methanol are used in this order. After ultrasonic cleaning for 10 minutes, it was dried. The arithmetic average roughness Ra of the FTO film was measured using a Dimension FastScan AFM Scanist Air mode according to Bruker in accordance with JIS B 0601-2001.
On the surface of the FTO film, a titanium isopropoxide ethanol solution adjusted to 2% by weight as an electron transport layer was applied by spin coating, and then baked at 500 ° C. for 10 minutes to produce a thin film layer. The film thickness of the thin film layer was 50 nm. Furthermore, a titanium oxide paste containing polyisobutyl methacrylate as an organic binder and titanium oxide (average particle size 16 nm) is laminated by the same spin coat method, and baked at 500 ° C. for 10 minutes. A 15 nm porous layer was produced. The electron transport layer (the sum of the thin film layer and the porous layer) had a thickness of about 300 nm. Then, PbI ₂ was dissolved in DMF to prepare a 1M solution. This was formed on the porous layer by spin coating. Furthermore, 1M solution was prepared by dissolving methylammonium iodide in propanol. An organic-inorganic hybrid semiconductor layer containing CH ₃ NH ₃ PbI ₃ was formed by immersing the above-described sample formed of PbI ₂ in this solution. Finally, as a hole transport layer, a solution in which Spiro-OMeTAD (having a spirobifluorene skeleton) was 68 mM, Tert-butylpyridine was 55 mM, and Lithium Bis (trifluoromethylsulfonyl) imide salt was dissolved by a spin coating method. The total film thickness of the electron transport layer, the organic / inorganic hybrid semiconductor layer, and the hole transport layer was 450 nm.
On the hole transport layer, a gold film having a thickness of 100 nm was formed as an anode by vacuum vapor deposition to obtain an organic-inorganic hybrid solar cell.

(Example 2)
In Example 1, the organic-inorganic hybrid solar cell was obtained like Example 1 except having used the glass substrate with the transparent electrode FTO adjusted to Ra = 15nm.

(Example 3)
In Example 1, the organic-inorganic hybrid solar cell was obtained like Example 1 except having used the glass substrate with the transparent electrode FTO adjusted to Ra = 22nm.

Example 4
In Example 1, a glass substrate with a transparent electrode ITO adjusted to Ra = 4.2 nm was used, and the thin film layer and the porous layer were each fired at 400 ° C. for 10 minutes. An inorganic hybrid solar cell was obtained.

(Example 5)
In Example 1, instead of using a glass substrate with a transparent electrode FTO, a polyimide (PI) film was formed on an Al foil by spin coating, and a Ti film was further formed on the polyimide film by vapor deposition. Obtained an organic-inorganic hybrid solar cell in the same manner as in Example 1.

(Example 6)
In Example 5, an organic-inorganic hybrid solar cell was obtained in the same manner as in Example 5 except that Ti foil was used instead of Al foil.

(Example 7)
In Example 4, an organic-inorganic hybrid solar cell was obtained in the same manner as in Example 4 except that a substrate in which ITO was formed on a resin (PET) base material was used.

(Comparative Example 1)
In Example 1, the organic-inorganic hybrid solar cell was obtained like Example 1 except having used the glass substrate with the transparent electrode FTO adjusted to Ra = 30nm.

(Comparative Example 2)
In Example 1, an organic-inorganic hybrid was used in the same manner as in Example 1 except that a glass substrate with a transparent electrode ITO adjusted to Ra = 27 nm was used and the thin film layer and the porous layer were each fired at 400 ° C. for 10 minutes. A solar cell was obtained.

(Comparative Example 3)
In Example 1, an organic-inorganic hybrid solar cell was obtained in the same manner as in Example 1 except that a layer made of antimony sulfide was used for the photoelectric conversion layer instead of the organic-inorganic hybrid semiconductor layer. The antimony sulfide layer was formed as follows. Antimony chloride and thiourea (molar ratio 1: 2) were dissolved in N, N-dimethylformamide, and the total concentration of antimony chloride and thiourea was adjusted to 20% by weight to prepare a coating solution for forming antimony sulfide. This was applied onto the porous layer by a spin coat method and dried to form a layer made of antimony sulfide.

(Comparative Example 4)
In Example 2, an organic-inorganic hybrid solar cell was obtained in the same manner as in Example 2 except that a layer made of antimony sulfide was used for the photoelectric conversion layer instead of the organic-inorganic hybrid semiconductor layer.

(Comparative Example 5)
In Example 3, an organic-inorganic hybrid solar cell was obtained in the same manner as in Example 3 except that a layer made of antimony sulfide was used for the photoelectric conversion layer instead of the organic-inorganic hybrid semiconductor layer.

(Comparative Example 6)
In Comparative Example 1, an organic-inorganic hybrid solar cell was obtained in the same manner as in Comparative Example 1, except that a layer made of antimony sulfide was used for the photoelectric conversion layer instead of the organic-inorganic hybrid semiconductor layer.

(Comparative Example 7)
In Example 5, instead of forming a polyimide film, a 10 wt% ethanol dispersion of Al ₂ O ₃ (average particle size 88 nm) was applied by spin coating and formed in the same manner as in Example 5. An organic-inorganic hybrid solar cell was obtained.

(Comparative Example 8)
In Comparative Example 7, an organic-inorganic hybrid solar cell was obtained in the same manner as Comparative Example 7 except that Ti foil was used instead of Al foil.

(Evaluation)
<Evaluation of leakage current (fill factor: FF)>
A power source (made by KEYTHLEY, 236 model) is connected between the electrodes of the organic-inorganic hybrid solar cell, and the fill factor of the organic-inorganic hybrid solar cell is measured using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) having an intensity of 100 mW / cm ^2. The leakage current was evaluated by measuring. The results are shown in Table 1 or 2.
For Examples 1 to 3 and Comparative Example 1, the value of the fill factor of Comparative Example 1 was relatively evaluated as 1, and for Examples 4, 7 and Comparative Example 2, the value of the fill factor of Comparative Example 2 was set to 1. Relative evaluation was performed, and the values of Example 5 and Comparative Example 7 were evaluated relative to the value of the fill factor of Comparative Example 7 as 1, and the values of Example 6 and Comparative Example 8 were compared to the value of the fill factor of Comparative Example 8 as 1. And about Comparative Examples 3-6, the value of the fill factor of the comparative example 6 was set to 1, and relative evaluation was carried out.
◎: The relative value of the fill factor is 1.3 times or more ○: The relative value of the fill factor is 1.2 times or more and less than 1.3 times △: The relative value of the fill factor is 1.1 times or more and less than 1.2 times × : Relative fill factor is less than 1.1 times

<Evaluation of light degradation>
A power source (manufactured by KEITHLEY, model 236) was connected between the electrodes of the solar cell, and light with an intensity of 100 mW / cm ² was irradiated using a solar simulation (manufactured by Yamashita Denso Co., Ltd.). The photoelectric conversion efficiency immediately after starting light irradiation and the photoelectric conversion efficiency after continuing light irradiation for 1 hour were measured, respectively. The photoelectric conversion efficiency after the light irradiation was continued for 1 hour / the value of the photoelectric conversion efficiency immediately after the light irradiation was started was determined and evaluated according to the following criteria.
○○○: Value is 0.9 or more ○○: Value is 0.8 or more and less than 0.9 ○: Value is 0.6 or more and less than 0.8 ×: Value is less than 0.6

About Comparative Examples 3-6, the inorganic semiconductor layer was used instead of the organic-inorganic hybrid semiconductor layer, and the effect of adjusting the arithmetic average roughness Ra of the electrode was not obtained.

According to the present invention, it is possible to provide an organic-inorganic hybrid solar cell that has low leakage current, excellent photoelectric conversion efficiency, and suppressed photodegradation.

1: Organic / inorganic hybrid solar cell 2: Substrate 3: Electrode 4: Thin film layer 5: Porous layer 6: Organic / inorganic hybrid semiconductor layer 7: Hole transport layer 8: Counter electrode 9: Metal thin film 10: Insulating material layer

Claims (7)

A substrate having an electrode whose surface has an arithmetic average roughness Ra of 25 nm or less, measured according to JIS B 0601-2001,
An electron transport layer;
An organic-inorganic hybrid semiconductor layer having a perovskite structure represented by a general formula R-M-X ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom);
An organic-inorganic hybrid solar cell comprising: The organic-inorganic hybrid solar cell according to claim 1, wherein the electron transport layer includes a thin film layer and a porous layer, and the thin film layer is disposed on the electrode side. Formula inorganic hybrid solar cell according to claim 1 or 2, wherein X in R-M-X ₃ is characterized in that it comprises a halogen atom. The organic-inorganic hybrid solar cell according to claim 1, 2 or 3, wherein the arithmetic average roughness Ra of the electrode is 20 nm or less. 5. The organic-inorganic hybrid solar cell according to claim 4, wherein the arithmetic average roughness Ra of the electrode is 15 nm or less. 6. The organic-inorganic hybrid solar cell according to claim 1, wherein the electrode is a transparent electrode or metal electrode made of ITO, FTO or ATO. 7. R in general formula R-M-X ₃ is methylamine, ethylamine, pentylcarboxyamine, formamidinium, guanidine or an ion thereof. Organic-inorganic hybrid solar cells.

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