JP2014195030A - Organic thin-film solar cell containing inclpc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic thin-film solar cell excellent in conversion efficiency and process of manufacturing the same.SOLUTION: An organic thin-film solar cell includes an InClPc containing layer. The InClPc containing layer is formed by evaporation while heating a substrate.

Description

  The present invention relates to an organic thin film solar cell containing InClPc.

  Organic solar cells (organic thin-film solar cells) provide electrical output with respect to light input, as typified by photodiodes and imaging devices that convert optical signals into electrical signals, and solar cells that convert optical energy into electrical energy. It is a device to show.

In recent years, solar cells have attracted a great deal of attention as a clean energy source against the background of fossil fuel depletion problems and global warming problems, and research and development have been actively conducted.
Conventionally, silicon solar cells represented by single crystal Si, polycrystal Si, amorphous Si, etc. have been put into practical use. However, as the cost and raw material Si shortage problems surface, The demand for next generation solar cells is increasing. Against this background, organic solar cells are attracting much attention as next-generation solar cells next to silicon-based solar cells because they are inexpensive, have low toxicity, and do not have a fear of shortage of raw materials.
An organic solar cell is composed of a pair of electrodes and an organic thin film layer sandwiched between the electrodes. Examples of the organic thin film layer include an n layer that transports electrons, a p layer that transports holes, and an i layer that is a mixed layer of a p-type material that transports holes and an n-type material that transports electrons.

High efficiency is demanded in organic solar cells and organic solar cell modules using the same. One method for increasing the efficiency is to increase the light absorption of the organic thin film layer.
Patent Document 1 uses InClPc for the i layer of a pin-type organic solar cell and H2Pc having light absorption on the shorter wavelength side than InClPc for the p layer, thereby improving the light absorption efficiency of the entire photoelectric conversion layer. However, in this invention, the i-layer containing InClPc (deposited at room temperature) does not absorb much at longer wavelengths. Therefore, InClPc can be combined only with a material having absorption in an extremely short wavelength region, and it is difficult to obtain high conversion efficiency.

  On the other hand, in Patent Documents 2 and 3, metal-free phthalocyanine (H2Pc) and perylene pigment are co-deposited while controlling the substrate temperature to form the i layer. However, the absorption wavelength of H2Pc hardly changes to the long wavelength side even when the substrate is heated, and it is difficult to obtain high conversion efficiency.

JP-A-6-318725 JP 2002-76027 A JP 2002-76391 A

  The objective of this invention is providing the organic thin-film solar cell with high conversion efficiency, and its manufacturing method.

According to one aspect of the present invention, there is provided an organic thin film solar cell including an InClPc-containing layer, wherein the InClPc-containing layer is produced by vapor deposition while heating a substrate. Is provided.
According to another aspect of the present invention, there is provided a method for manufacturing an organic thin film solar cell including an InClPc-containing layer, wherein the InClPc-containing layer is formed by vapor deposition while heating a substrate. Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, an organic thin-film solar cell with high conversion efficiency and its manufacturing method can be provided.

It is a figure which shows the relationship between the substrate temperature at the time of an InClPc film | membrane vapor deposition, and the peak intensity of a light absorbency. It is a figure which shows the relationship between the substrate temperature at the time of H2Pc film vapor deposition, and the peak intensity of a light absorbency. It is a figure which shows the spectral sensitivity spectrum of the organic thin-film solar cell obtained in Example 1 and Comparative Example 1. It is a figure which shows the spectral sensitivity spectrum of the organic thin film solar cell obtained by Example 2, 3 and the comparative example 2. FIG.

The organic thin film solar cell of one embodiment of the present invention has a layer containing InClPc having the following structure, and this layer is produced by vapor deposition while heating a substrate.
When InClPc is deposited while heating the substrate, the InClPc-containing layer has absorption sensitivity in the long wavelength region. As a result, the organic thin-film solar cell including such an InClPc-containing layer has increased absorption in the long wavelength region and improved conversion efficiency.

  The InClPc-containing layer can function as an active layer. For example, when the organic thin-film solar cell is a pn-type organic thin-film solar cell or a pin-type organic thin-film solar cell, the InClPc-containing layer can be used as a p-layer. Moreover, it can mix with n material and can be set as i layer. One organic thin film solar cell can be used for both the p layer and the i layer.

  The heating temperature of a board | substrate can be 40 degreeC or more, for example. Preferably it is 45 degreeC or more, More preferably, it is 50 degreeC or more. Although an upper limit is not specifically limited as long as the effect of this invention is acquired, Usually, it is 150 degrees C or less, Preferably it is 120 degrees C or less. When the heating temperature is high, the absorption sensitivity becomes longer. However, if the heating temperature is too high, crystallization of InClPc is likely to be promoted, and the solar cell may not function due to large crystal grains.

The organic thin film solar cell according to one embodiment of the present invention is not particularly limited as long as it has a structure including an InClPc-containing layer between a pair of electrodes. Specifically, the structure which has the following structure on a board | substrate is mentioned.
(1) Lower electrode / p layer / n layer / upper electrode (2) Lower electrode / p layer / i layer (or a mixed layer of p material and n material) / n layer / upper electrode (3) Lower electrode / p material N layer mixed layer / upper electrode In the above configurations (1) and (2), the p layer and the n layer may be replaced.

Moreover, you may provide a buffer layer between an electrode and an organic layer as needed. For example, as a specific example, when a buffer layer is provided in the configuration (1), a structure having the following configuration can be given.
(4) Lower electrode / buffer layer / p layer / n layer / upper electrode (5) Lower electrode / p layer / n layer / buffer layer / upper electrode (6) Lower electrode / buffer layer / p layer / n layer / buffer Layer / Top electrode

The InClPc-containing layer may be formed of InClPc alone or may contain other components. It is preferable to contain 20% by weight or more. About another mixed material, the well-known material used with an organic thin film solar cell can be used. Moreover, the member which comprises organic thin film solar cells other than an InClPc content layer can use the well-known member used with an organic thin film solar cell.
Hereinafter, each component will be briefly described.

[substrate]
An organic thin film solar cell is usually formed on a substrate. The substrate is preferably one having mechanical and thermal strength and transparency. For example, there are a glass substrate and a transparent resin film. Transparent resin films include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone. , Polysulfone, polyethersulfone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, Polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimide, polyetherimide, polyimide, polypropylene, etc. It is.
In the case of an opaque substrate, the opposite electrode (that is, the electrode far from the substrate) is preferably a transparent electrode or a translucent electrode.

[Lower and upper electrodes]
The material for the lower electrode and the upper electrode is not particularly limited, and a known conductive material can be used. For example, a metal such as tin-doped indium oxide (ITO), gold (Au), osmium (Os), palladium (Pd) can be used as the electrode connected to the p layer, and silver as the electrode connected to the n layer. Metals such as (Ag), aluminum (Al), indium (In), calcium (Ca), platinum (Pt), lithium (Li) and the like, and binary metal systems such as Mg: Ag, Mg: In and Al: Li, Furthermore, the electrode example material connected with the said P layer can be used.
In order to obtain highly efficient photoelectric conversion characteristics, for example, when the organic thin film solar cell is a solar cell, it is desirable that at least one surface of the solar cell is sufficiently transparent in the solar spectrum. The transparent electrode is formed using a known conductive material so as to ensure a predetermined translucency by a method such as vapor deposition or sputtering. The light transmittance of the electrode on the light receiving surface is preferably 10% or more. In a preferred configuration of the pair of electrode configurations, one of the electrode portions includes a metal having a high work function, and the other includes a metal having a low work function.

[Active layer (p layer, n layer, i layer)]
When the InClPc-containing layer is used for the p layer, the n layer is not particularly limited, but a compound having a function as an electron acceptor is preferable. For example, if the organic compound include fullerene derivatives such as C _60, C _70, carbon nanotube, perylene derivatives, polycyclic quinone, and quinacridone. A material having high electron mobility is preferred. Further, a material having a small electron affinity is preferable. Thus, a sufficient open-circuit voltage can be realized by combining materials having a small electron affinity as the n layer.

When an inorganic compound is used as the material for the n layer, an n-type inorganic semiconductor compound can be used. Specifically, doping semiconductors and compound semiconductors such as n-Si, GaAs, CdS, PbS, CdSe, InP, Nb ₂ O ₅ , WO ₃ , Fe ₂ O ₃ , titanium dioxide (TiO ₂ ), monoxide Examples include titanium oxide such as titanium (TiO) and dititanium trioxide (Ti ₂ O ₃ ), and conductive oxides such as zinc oxide (ZnO) and tin oxide (SnO ₂ ). You may use combining more than a seed. Preference is given to using titanium oxide, particularly preferably titanium dioxide.

  When the InClPc-containing layer is used for the i layer, the i layer can be formed by mixing with the n-layer compound.

[Buffer layer]
In general, an organic thin film solar cell often has a thin total film thickness, and therefore, the upper electrode and the lower electrode are short-circuited, and the yield of cell fabrication is often reduced. In such a case, it is preferable to prevent this by laminating a buffer layer.
As a preferable compound for the buffer layer, a compound having sufficiently high carrier mobility is preferable so that the short-circuit current does not decrease even when the film thickness is increased. For example, if it is a low molecular compound, the aromatic cyclic acid anhydride represented by NTCDA shown below etc. will be mentioned, and if it is a high molecular compound, poly (3,4-ethylenedioxy) thiophene: polystyrene sulfonate (PEDOT: PSS), polyaniline: camphorsulfonic acid (PANI: CSA), and other known conductive polymers. If it is an inorganic compound, a metal oxide such as molybdenum oxide (MoO ₃ ) may be used.

(In PEDOT: PSS, n and m are the number of repetitions.)

  The buffer layer can also have a role of preventing excitons from diffusing to the electrode and being deactivated. Inserting a buffer layer as an exciton blocking layer in this way is effective for increasing efficiency. The exciton blocking layer can be inserted on either the anode side or the cathode side, or both can be inserted simultaneously. In this case, as a preferable material for the exciton blocking layer, for example, a well-known material for a hole barrier layer or a material for an electron barrier layer for use in an organic electroluminescence element (organic EL element) can be used.

  A preferable material for the hole blocking layer is a compound having a sufficiently large ionization potential, and a preferable material for the electron blocking layer is a compound having a sufficiently small electron affinity. Specifically, bathocuproin (BCP), bathophenanthroline (BPhen), and the like, which are well-known materials for organic EL device applications, can be used as the cathode-side hole barrier layer material.

For the buffer layer, the inorganic semiconductor compounds exemplified as the n-layer material may be used. As the p-type inorganic semiconductor compound, CdTe, p-Si, SiC, GaAs, WO ₃ or the like can be used.

[Method of manufacturing organic thin film solar cell]
The InClPc-containing layer is formed by vapor deposition, but the other layers of the organic thin film solar cell are formed by dry film formation methods such as vacuum vapor deposition, sputtering, plasma, ion plating, spin coating, dip coating, casting, roll coating, Wet film formation methods such as flow coating and ink jet can be applied.

  The thickness of each layer is not particularly limited, but is set to an appropriate thickness. Since it is generally known that the exciton diffusion length of an organic thin film is short, if the film thickness is too thick, the exciton is deactivated before reaching the heterointerface, resulting in low photoelectric conversion efficiency. If the film thickness is too thin, pinholes and the like are generated, so that sufficient diode characteristics cannot be obtained, resulting in a decrease in conversion efficiency. The normal film thickness is suitably in the range of 1 nm to 10 μm, but more preferably in the range of 5 nm to 0.2 μm.

  In the case of the dry film forming method, a known resistance heating method is preferable, and for forming the mixed layer, for example, a film forming method by simultaneous vapor deposition from a plurality of evaporation sources is preferable. More preferably, the substrate temperature is controlled during film formation.

  In the case of a wet film forming method, a material for forming each layer is dissolved or dispersed in an appropriate solvent to prepare a light-emitting organic solution to form a thin film, and any solvent can be used. For example, halogenated hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, trichloroethane, chlorobenzene, dichlorobenzene, chlorotoluene, ether solvents such as dibutyl ether, tetrahydrofuran, dioxane, anisole, methanol, Alcohol solvents such as ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, hexane, octane, decane, tetralin, Examples include ester solvents such as ethyl acetate, butyl acetate, and amyl acetate. Of these, hydrocarbon solvents or ether solvents are preferable. These solvents may be used alone or in combination. In addition, the solvent which can be used is not limited to these.

In any organic compound layer of the organic thin film solar cell, an appropriate resin or additive may be used for improving the film formability and preventing pinholes in the film.
Usable resins include polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethyl methacrylate, polymethyl acrylate, cellulose and other insulating resins and copolymers thereof, poly-N-vinyl. Examples thereof include photoconductive resins such as carbazole and polysilane, and conductive resins such as polythiophene and polypyrrole.
Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

Experimental Example InClPc was deposited on a quartz substrate at substrate temperatures of 25 ° C., 50 ° C., and 90 ° C. to produce a film having a thickness of 100 nm. The absorbance of the film was measured. The results are shown in FIG. For reference, the absorbance of a C60 film prepared by vapor deposition at a substrate temperature of 25 ° C. is also shown.
FIG. 1 shows that the peak intensity on the long wavelength side is increased by setting the substrate temperature to 50 ° C. and 90 ° C.

H2Pc was vapor-deposited at a substrate temperature of 25 ° C. and 90 ° C. on a quartz substrate to produce a film with a thickness of 50 nm, and the absorbance was measured. The results are shown in FIG.
FIG. 2 shows that the absorption wavelength hardly changes even when the substrate temperature is 90.degree.
Therefore, it can be said that the effect of having absorption sensitivity in the long wavelength region is an effect peculiar to InClPc.

Example 1
A glass substrate with an ITO transparent electrode (lower electrode) having a thickness of 25 mm × 75 mm × 0.7 mm was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes, and then UV ozone cleaning was performed for 30 minutes.
The glass substrate with a transparent electrode line after washing was mounted on a substrate holder of a vacuum deposition apparatus. After heating the substrate to 90 ° C., a 15 nm-thick InClPc film is formed at 0.2 Å / s by resistance heating vapor deposition so as to cover the transparent electrode on the surface on which the transparent electrode line is formed. Filmed. Substrate heating was performed by flowing a heating fluid through a metal medium in contact with the substrate holder. The substrate temperature was measured by attaching a thermocouple to the substrate.
Next, the substrate was cooled to 25 ° C. or lower, and a C60 film having a thickness of 40 nm was formed on the InClPc film by resistance heating vapor deposition at 0.5 Å / s.

Subsequently, 10 nm bathocuproine (BCP) was deposited at 0.5 蒸 着 / s by resistance heating vapor deposition. Finally, metal Al was deposited as a counter electrode with a thickness of 80 nm to produce an organic solar cell. The element area was 1 cm ² .

The element structure is shown below (the numerical value in parenthesis represents the film thickness (nm)).
ITO / InClPc (15) / C60 (40) / BCP (10) / Al (80)

  The spectral sensitivity spectrum of the obtained organic thin film solar cell is shown in FIG.

Comparative Example 1
An organic thin film solar cell was fabricated in the same manner as in Example 1 except that the InClPc layer was formed while maintaining the substrate temperature at room temperature (25 ° C.). The spectral sensitivity spectrum of the obtained organic thin film solar cell is shown in FIG.
FIG. 3 shows that Example 1 has sensitivity on the longer wavelength side.

Example 2
As in Example 1, the cleaned glass substrate with an ITO transparent electrode is mounted on a substrate holder of a vacuum evaporation apparatus, and MoO ₃ having a thickness of 10 nm is formed by resistance heating evaporation so as to cover the transparent electrode. The film was formed with s. The substrate was heated to 50 ° C., and InClPc was formed thereon by resistance heating vapor deposition at 0.2 Å / s to form a p-layer having a thickness of 5 nm. The substrate was kept at 50 ° C., and InClPc was co-evaporated to 0.2 nm / s to 5 nm and C60 to 0.8 nm / s to 20 nm to form an i layer.

The substrate was cooled to 25 ° C. or lower, and a 40 nm C60 layer and a 10 nm bathocuproine (BCP) layer were formed at 0.5 Å / s by resistance heating vapor deposition. Finally, metal Al was deposited as a counter electrode with a thickness of 80 nm to produce an organic solar cell. The element area was 1.0 cm ² .

The element structure is shown below (the numerical value in parenthesis represents the film thickness (nm)).
ITO / MoO ₃ (10) / InClPc (5) / InClPc: C60 (ratio 1: 4) (25) / C60 (40) / BCP (10) / Al (80)

  The spectral sensitivity spectrum of the obtained organic thin film solar cell is shown in FIG.

Furthermore, about the organic solar cell, the IV characteristic was measured on AM1.5 conditions (light intensity (Pin) 100mW / cm < ² >). Table 1 shows the open-circuit voltage (Voc), the short-circuit current density (Jsc), the fill factor (FF), and the photoelectric conversion efficiency (η).

The photoelectric conversion efficiency (η) was obtained by the following formula.
(Where Voc is the open circuit voltage, Jsc is the short circuit current density, FF is the fill factor, and Pin is the incident light energy.)

Example 3
An organic thin-film solar cell was fabricated in the same manner as in Example 2 except that the substrate temperature was maintained at 90 ° C. and the InClPc layer and the InClPc: C60 layer were formed. The spectral sensitivity spectrum of the obtained organic thin film solar cell is shown in FIG. The element characteristics were measured in the same manner as in Example 2, and the results are shown in Table 1.

Comparative Example 2
An organic thin film solar cell was fabricated in the same manner as in Example 2 except that the InClPc layer and the InClPc: C60 layer were formed while maintaining the substrate temperature at room temperature (25 ° C.). The spectral sensitivity spectrum of the obtained organic thin film solar cell is shown in FIG. The element characteristics were measured in the same manner as in Example 2, and the results are shown in Table 1.

FIG. 4 shows that the contribution of absorption on the long wavelength side increases as the substrate temperature increases.
Further, it can be seen from Table 1 that the conversion efficiency improves as the light absorption on the long wavelength side increases.

  The organic solar cell of the present invention can be used as a power source or auxiliary power source for various devices such as watches, mobile phones and mobile personal computers, and electrical appliances. Combined with a rechargeable battery with a charging function, it can be used in the dark, and the application can be expanded.

Claims (10)

An organic thin film solar cell including an InClPc-containing layer,
An organic thin film solar cell in which the InClPc-containing layer is produced by vapor deposition while heating a substrate.   The organic thin film solar cell according to claim 1, wherein the InClPc-containing layer is one or more layers selected from a p layer and an i layer.   The organic thin-film solar cell according to claim 2, wherein the i layer contains fullerenes.   The organic thin-film solar cell according to any one of claims 1 to 3, wherein the heating temperature of the substrate is 40 ° C or higher.   The organic thin film solar cell according to claim 4, wherein the heating temperature of the substrate is 120 ° C. or less. A method for producing an organic thin-film solar cell including an InClPc-containing layer,
A method for producing an organic thin film solar cell, wherein the InClPc-containing layer is formed by vapor deposition while heating a substrate.   The method for producing an organic thin film solar cell according to claim 6, wherein the InClPc-containing layer is one or more layers selected from a p layer and an i layer.   The manufacturing method of the organic thin-film solar cell of Claim 7 in which the said i layer contains fullerenes.   The method for producing an organic thin-film solar cell according to any one of claims 6 to 8, wherein a heating temperature of the substrate is 40 ° C or higher.   The method for producing an organic thin film solar cell according to claim 9, wherein the heating temperature of the substrate is 120 ° C. or less.