WO2009110075A1

WO2009110075A1 - Organic semiconductor element

Info

Publication number: WO2009110075A1
Application number: PCT/JP2008/053978
Authority: WO
Inventors: 崇人小山田
Original assignee: パイオニア株式会社
Priority date: 2008-03-05
Filing date: 2008-03-05
Publication date: 2009-09-11
Also published as: TW200950172A

Abstract

This invention provides an organic semiconductor element comprising a pair of opposed first and second electrodes and a plurality of organic semiconductor layers disposed in a stacked state between the first and second electrodes. The second electrode is a negative electrode. An electron transport organic semiconductor layer, which is in contact with the interface of the organic semiconductor layer and is formed of an organic semiconductor doped with a metal acid salt compound in which an electron donating metal is a counter cation, is provided between the second electrode and the organic semiconductor layer.

Description

Organic semiconductor device

The present invention relates to an organic semiconductor element, and more particularly to an organic semiconductor element using an organic compound having a charge transporting property (hole or electron mobility) and having an organic semiconductor layer made of such a compound.

There is an organic solar cell using an organic material as one of the organic semiconductor elements. Inorganic solar cells using p-type and n-type semiconductors made of inorganic materials such as silicon for the photoelectric conversion layer are mainly used because of high energy conversion efficiency, but p-type organic semiconductors and n-type organic semiconductors are used instead of inorganic semiconductors. Research and development of lightweight, inexpensive, and flexible organic solar cells continues. As organic solar cells, dye-sensitized solar cells (Gretzel cells), organic thin-film solar cells, and the like are known. Dye-sensitized solar cells are wet, and organic thin-film solar cells are all solid.

Solar cells, whether organic or inorganic, first absorb solar energy (light collection) and are excited to a high energy state to generate electrons and holes, which are then transferred to the negative electrode (electron transport). Electrical energy is generated by transporting the holes to the positive electrode (hole transport). Organic thin-film solar cells differ greatly from inorganic solar cells in the generation mechanism of electrons and holes. In inorganic solar cells represented by silicon, electrons and holes are generated at the p-type and n-type semiconductor interfaces simultaneously with light absorption and move to the respective electrodes. Excitons whose holes are strongly bound are generated in the light collection layer and move to the interface with the electron transport layer or the hole transport layer, so that electrons and holes are generated. Therefore, in order to improve the device performance of the organic solar cell, it is important to efficiently transport excitons generated in the light collection layer to the interface, and the organic solar cell uses an organic compound having a charge transporting property. It has a multilayer structure (see Patent Document 1).

Meanwhile, an organic thin film transistor is one of organic semiconductor elements. In recent years, research and development has been actively conducted, and among these, researches on organic active light emitting devices in which organic electroluminescence devices and organic electroluminescence (EL) devices are driven in an active matrix by organic thin film transistors are being conducted.

In an organic active light-emitting device, for example, a transparent gate electrode is provided on a substrate, a transparent gate insulating film is formed thereon so as to cover the gate electrode, and a source electrode (charge injection) having an opening on the gate insulating film And an organic semiconductor film, an organic EL film is laminated on the organic semiconductor film, and a drain electrode (charge injection) is laminated thereon (see Patent Document 2).

Generally, the organic EL film has a structure in which a plurality of organic material layers including an organic light emitting layer are stacked. In addition to the organic light emitting layer, the organic material layer has a layer made of a material having a hole transport ability such as a hole injection layer and a hole transport layer, and an electron transport ability such as an electron transport layer and an electron injection layer. Layers made of materials are included. The electron injection layer includes an inorganic compound.

When an electric field is applied to the organic light-emitting layer and the organic EL film of the electron or hole transport layer stack, holes are injected from the source electrode and electrons are injected from the drain electrode. When combined, excitons are formed and emit light when returning to the ground state. In order to improve the light emission efficiency, it is important to efficiently transport carriers such as electrons to the interface, and the organic active light emitting device has a multilayer structure using an organic compound having a charge transporting property.

As described above, it is effective to provide a charge injection layer in order to increase the efficiency of power generation and light emission of an organic semiconductor device having an organic semiconductor layer made of a charge transporting organic compound. There is a need. A highly efficient organic semiconductor element that can be continuously driven is desired.
JP 2006-156956 A JP2007-200788 JP 2002-367784 A JP 2006-148134 A

In order to improve the electron injection efficiency of conventional organic semiconductor elements, for example, organic EL elements, alkali metals and alkaline earth metals having low work functions, compounds thereof (CsF, Cs ₂ CO ₃ , Li ₂ O, LiF), etc. Have been used for inorganic electron injection layers. However, these materials are difficult to handle because they are easily oxidized, decomposed (Cs ₂ CO ₃ ) depending on the material, and have deliquescence. Moreover, since these have high reactivity, there also exists a problem which reacts with a vapor deposition boat and corrodes. (See Patent Document 3)
In the case where Cs simple substance is formed with conventional electron injection materials, Cs simple substance is a conductive metal, but because of its high reactivity, it becomes Cs ₂ O cesium oxide during film formation by vacuum deposition. ing.

In addition, there is an example in which a metal acid salt compound is used as an inorganic layer in the inorganic electron injection layer of the organic EL element (see Patent Document 4). This can be expected to have an electron injection effect by the metal acid salt compound, but Cs ₂ MoO ₄ From this example, the driving voltage decreases with the film thickness of a specific metalate compound, but when the film thickness exceeds a certain film thickness, the driving voltage of the element increases.

In the organic EL element disclosed in Patent Document 3, alkali metal and conductive metal oxide are co-evaporated. Similarly, when the film thickness exceeds a certain value, the driving voltage of the element increases.

Conventionally, when doping an alkali metal, alkaline earth metal or a compound thereof having a low work function, there are the problems mentioned above. In particular, Cs alone has a melting point of 23 degrees and its molecular weight is low. When the element is stored and stored at high temperature, it is considered that Cs may diffuse and lead to element deterioration. If it will be in such a state, the drive life of an organic-semiconductor element will become short as a result.

Therefore, the problem to be solved by the invention is, for example, to provide an organic semiconductor element such as an organic EL element capable of extending the life.

An organic semiconductor device according to the present invention is an organic semiconductor device including a plurality of organic semiconductor layers stacked between a pair of opposed first and second electrodes, wherein the second electrode is a negative electrode, An electron transporting organic semiconductor layer made of an organic semiconductor that is in contact with the interface of the organic semiconductor layer and doped with a metal acid salt compound having an electron donating metal as a counter cation between the second electrode and the organic semiconductor layer. It is characterized by having. Since the electron-transporting organic semiconductor layer is provided, the device life can be improved. The electron-transporting organic semiconductor layer can efficiently inject electrons even in a cathode having a high work function of 4.5 eV or more. Since the electron transporting organic semiconductor layer is used, there is an effect that the electron injection layer is unnecessary. That is, since the electron transporting organic semiconductor layer is in contact with the cathode, electrons can be injected. The electron transporting organic semiconductor layer has an effect that the metal salt compound does not diffuse under high temperature storage.

In the organic semiconductor device of the present invention, the electron donating metal is one or more metals selected from metals having a work function of 3.5 eV or less among transition metals including alkali metals, alkaline earth metals, and rare earth metals. Can consist of:

In the organic semiconductor element of the present invention, the concentration of the metal salt compound in the electron transporting organic semiconductor layer can be 0.1 to 40% by weight. When the electron transporting organic semiconductor layer has a specific concentration or a certain concentration or more, it has an effect of reducing the driving voltage of the element.

In the organic semiconductor element of the present invention, the electron transporting organic semiconductor layer may have a thickness of 1 nm to 300 nm.

In the organic semiconductor element of the present invention, the electron transporting organic semiconductor layer can be formed by single vapor deposition or multiple vapor deposition. Since the metal salt compound only needs to be vapor-deposited, the process is simplified.

In the organic semiconductor element of the present invention, the electron transporting organic semiconductor layer film may have a transmittance of 50% or more.

In the organic semiconductor element of the present invention, the metal acid salt compound may include a conductive oxide semiconductor.

In the organic semiconductor element of the present invention, the conductive oxide semiconductor has a carrier mobility of 1 × 10 ⁻¹⁰ to 1 × 10 ¹⁰ cm ² / Vs or a conductivity of 10 ¹⁰ to 10 ⁻¹⁰ Ω · cm. Can have.

In the organic semiconductor device of the present invention, the organic semiconductor may have a carrier mobility of 1 × 10 ⁻¹⁰ to 1 × 10 ¹⁰ cm ² / Vs.

In the organic semiconductor element of the present invention, the plurality of organic semiconductor layers include a light emitting layer, and one of the first and second electrodes is translucent or transparent, or the first and second electrodes are It can be an organic electroluminescent device that is transparent. The driving voltage of the organic electroluminescent element is lowered, and the consumption voltage of the organic electroluminescent element panel is reduced. Moreover, the calorific value of a panel can be suppressed by reducing the power consumption of a panel. By doping an organic semiconductor layer with an alkali metal or alkaline earth metal having a low work function or a compound thereof (CsF, Cs ₂ CO ₃ , Li ₂ O, LiF) or the like, an electron can be obtained without inserting an inorganic electron injection layer. Since it can be composed of a transportable organic semiconductor layer and a cathode (Al, etc.) and the driving voltage is reduced and there is no need to insert an inorganic electron injection layer, it can be made thinner by the thickness of the electron injection layer. The process can be simplified and the power consumption of the element can be reduced.

In the organic semiconductor element of the present invention, the plurality of organic semiconductor layers may be organic solar cells including a light collection layer and at least one of an electron transport layer and a hole transport layer.

It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the drive voltage change with respect to the doping density | concentration to the organic-semiconductor layer of the metal salt compound in the organic electroluminescent element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the drive voltage change with respect to the doping density | concentration to the organic-semiconductor layer of the metal salt compound in the organic electroluminescent element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the emitted light intensity change with respect to the drive elapsed time in the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the drive voltage change with respect to the drive elapsed time in the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the current density-driving voltage characteristic in the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a graph which shows the current density-driving voltage characteristic in the organic EL element of the organic-semiconductor element of other embodiment by this invention. It is a diagram which shows the front of the element before and after the start of an atmospheric exposure experiment of the organic EL element of the organic semiconductor element of embodiment by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole block layer 7 Electron transporting organic semiconductor layer 8 Cathode

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the organic semiconductor element of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an example of the organic EL element of the present embodiment includes, in order, a transparent first electrode (anode) 2, a hole transport layer 4 made of an organic compound, on a transparent substrate 1 such as glass, An organic light emitting layer 5 made of an organic compound, an electron transporting organic semiconductor layer 7 made of an organic compound, and a second electrode (cathode that is a negative electrode) 8 made of a metal are laminated. That is, in the organic EL element, a pair of first and second electrodes facing each other correspond to an anode and a cathode, and a plurality of organic semiconductor layers stacked between them are a hole injection layer, a hole transport layer, Includes a light emitting layer. An electron-transporting organic semiconductor layer is disposed between the cathode of the second electrode and the organic semiconductor layer (light-emitting layer) in contact with the interface of the light-emitting layer, which is doped with a metal salt compound having an electron-donating metal as a counter cation. Made of organic semiconductor.

As shown in FIG. 1, in addition to the structure of anode 2 / hole injection layer 3 / hole transport layer 4 / light emitting layer 5 / electron transporting organic semiconductor layer 7 / cathode 8 /, as shown in FIG. The structure of anode 2 / hole injection layer 3 / light emitting layer 5 / electron transporting organic semiconductor layer 7 / cathode 8 /, as shown in FIG. 3, anode 2 / hole transport layer 4 / light emitting layer 5 / electron transport The structure of the conductive organic semiconductor layer 7 / cathode 8 / and the structure of the anode 2 / light emitting layer 5 / electron transporting organic semiconductor layer 7 / cathode 8 / as shown in FIG. The organic EL element by this invention should just have the electron transport organic-semiconductor layer 7 in the interface with the cathode 8. FIG. Therefore, the electron transporting organic semiconductor layer 7 adjacent layer is not limited to the light emitting layer, and a block layer and / or a buffer layer between the light emitting layer and the electron transporting organic semiconductor layer, for example, as shown in FIG. In addition to the structure of anode 2 / hole injection layer 3 / hole transport layer 4 / light emitting layer 5 / hole blocking layer 6 / electron transporting organic semiconductor layer 7 / cathode 8 /, as shown in FIG. The structure of anode 2 / hole injection layer 3 / light emitting layer 5 / hole blocking layer 6 / electron transporting organic semiconductor layer 7 / cathode 8 /, as shown in FIG. 7, anode 2 / hole transport layer 4 / The structure of the light emitting layer 5 / hole blocking layer 6 / electron transporting organic semiconductor layer 7 / cathode 8 /, and as shown in FIG. 8, the anode 2 / light emitting layer 5 / hole blocking layer 6 / electron transporting organic semiconductor The configuration of layer 7 / cathode 8 / is also included in the present invention.

--Substrate and first and second electrodes--
In addition to the glass transparent material of the substrate 1, in addition to a translucent material such as a plastic material such as polystyrene, an opaque material such as silicon or Al, a thermosetting resin such as a phenol resin, a thermoplastic resin such as a polycarbonate, etc. Can be used.

As electrode materials of the first electrode (anode) 2 and the second electrode (cathode) 8, Ti, Al, Al, Cu, Ni, Ag, Mg: Ag, Au, Pt, Pd, Ir, Cr, Mo, W And metals such as Ta and alloys thereof. Alternatively, a conductive polymer such as polyaniline or PEDT: PSS can be used. Alternatively, an oxide transparent conductive thin film, for example, one containing indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide, tin oxide or the like as a main composition can be used. The thickness of each electrode is preferably about 10 to 500 nm. These electrode materials are preferably produced by vacuum deposition or sputtering.

A conductive material having a work function larger than that of the second electrode (cathode) 8 is selected for the first electrode (anode) 2 as the positive electrode. Further, the materials of the first and second electrodes are selected so that the light emission side is transparent or translucent. In particular, it is preferable to select a material in which one or both of the first and second electrodes have a transmittance of at least 10% at the emission wavelength obtained from the organic light emitting material.

--- Organic semiconductor layer--
The organic semiconductor layer constituting the main components of the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, and the electron transport organic semiconductor layer 7 has a charge transport property (hole and / or electron mobility). Utilizes organic compounds.

Examples of the organic compound having an electron transporting property as a main component of the light emitting layer and the electron transporting organic semiconductor layer include polycyclic compounds such as p-terphenyl and quaterphenyl and derivatives thereof, naphthalene, tetracene, pyrene, coronene, chrysene Condensed polycyclic hydrocarbon compounds such as anthracene, diphenylanthracene, naphthacene, phenanthrene and their derivatives, condensed heterocyclic compounds such as phenanthroline, bathophenanthroline, phenanthridine, acridine, quinoline, quinoxaline, phenazine and their derivatives, Fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, oxadiazole, aldazine, bisbenzoxazoline, biphenyl Styryl, pyrazine, cyclopentadiene, oxine, aminoquinoline, imine, diphenylethylene, vinyl anthracene, diaminocarbazole, pyran, may be mentioned thiopyran, polymethine, merocyanine, quinacridone, rubrene, and the like, and their derivatives etc..

Further, as an organic compound having an electron transporting property, a metal chelate complex compound, particularly a metal chelated oxanoid compound, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis [benzo (f) -8-quinolinolato Zinc, bis (2-methyl-8-quinolinolato) aluminum, tris (8-quinolinolato) indium, tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-8- There may also be mentioned metal complexes having at least one 8-quinolinolato or a derivative thereof such as quinolinolato) gallium and bis (5-chloro-8-quinolinolato) calcium as a ligand.

Also, as organic compounds having electron transport properties, oxadiazoles, triazines, stilbene derivatives, distyrylarylene derivatives, styryl derivatives, and diolefin derivatives can be suitably used.

Further, as an organic compound that can be used as an organic compound having an electron transporting property, 2,5-bis (5,7-di-t-benzyl-2-benzoxazolyl) -1,3,4-thiazole, 4, 4'-bis (5,7-t-pentyl-2-benzoxazolyl) stilbene, 4,4'-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazoly Ru] stilbene, 2,5-bis (5.7-di-t-pentyl-2-benzoxazolyl) thiophene, 2,5-bis [5- (α, α-dimethylbenzyl) -2-benzoxa Zolyl] thiophene, 2,5-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl] -3,4-diphenylthiophene, 2,5-bis (5- Methyl-2-benzoxazolyl) thiophene, 4,4 ′ -Bis (2-benzoxazolyl) biphenyl, 5-methyl-2- {2- [4- (5-methyl-2-benzoxazolyl) phenyl] vinyl} benzoxazole, 2- [2- (4 Benzoxazoles such as -chlorophenyl) vinyl] naphtho (1,2-d) oxazole, benzothiazoles such as 2,2 '-(p-phenylenedipinylene) -bisbenzothiazole, 2- {2- [4 -(2-Benzimidazolyl) phenyl] vinyl} benzimidazole, 2- [2- (4-carboxyphenyl) vinyl] benzimidazole and the like can also be mentioned.

Further, as an organic compound having an electron transporting property, 1,4-bis (2-methylstyryl) benzene, 1,4-bis (3-methylstyryl) benzene, 1,4-bis (4-methylstyryl) benzene, Distyrylbenzene, 1,4-bis (2-ethylstyryl) benzene, 1,4-bis (3-ethylstyryl) benzene, 1,4-bis (2-methylstyryl) -2-methylbenzene, 1,4 Examples thereof include -bis (2-methylstyryl) -2-ethylbenzene.

Further, as an organic compound having an electron transporting property, 2,5-bis (4-methylstyryl) pyrazine, 2,5-bis (4-ethylstyryl) pyrazine, 2,5-bis [2- (1- Naphthyl) vinyl] pyrazine, 2,5-bis (4-methoxystyryl) pyrazine, 2,5-bis [2- (4-biphenyl) vinyl] pyrazine, 2,5-bis [2- (1-pyrenyl) vinyl ] Pyrazine etc. are mentioned.

Other organic compounds having electron transport properties include 1,4-phenylene dimethylidin, 4,4'-phenylene dimethylidin, 2,5-xylylene dimethylidin, and 2,6-naphthylene dimethylidene. Din, 1,4-biphenylenedimethylidin, 1,4-p-terephenylenedimethylidin, 9,10-anthracenediyldimethylidin, 4,4 '-(2,2-di-t-butylphenylvinyl Known materials conventionally used for the production of organic EL devices such as biphenyl and 4,4 ′-(2,2-diphenylvinyl) biphenyl can be appropriately used.

On the other hand, organic compounds having hole transporting properties include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl, N, N′-diphenyl-N, N′-di (3-methyl Phenyl) -4,4′-diaminobiphenyl, 2,2-bis (4-di-p-tolylaminophenyl) propane, N, N, N ′, N′-tetra-p-tolyl-4,4′- Diaminobiphenyl, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N′-diphenyl-N, N′-di (4-methoxyphenyl) -4,4′-diaminobiphenyl, N, N, N ′, N′-tetraphenyl-4,4′-diaminodiphenyl ether, 4,4′-bis (diphenylamino) quadriphenyl, 4-N, N-diphenylamino- (2-diphenylvinyl) benzene, 3- Toxi-4′-N, N-diphenylaminostilbenzene, N-phenylcarbazole, 1,1-bis (4-di-p-triaminophenyl) -cyclohexane, 1,1-bis (4-di-p- Triaminophenyl) -4-phenylcyclohexane, bis (4-dimethylamino-2-methylphenyl) -phenylmethane, N, N, N-tri (p-tolyl) amine, 4- (di-p-tolylamino)- 4 ′-[4 (di-p-tolylamino) styryl] stilbene, N, N, N ′, N′-tetra-p-tolyl-4,4′-diamino-biphenyl, N, N, N ′, N ′ -Tetraphenyl-4,4'-diamino-biphenyl N-phenylcarbazole, 4,4'-bis [N- (1-naphthyl) -N-phenyl-amino] biphenyl, 4,4 ''-bis [N (1-naphthyl) -N-phenyl-amino] p-terphenyl, 4,4'-bis [N- (2-naphthyl) -N-phenyl-amino] biphenyl, 4,4'-bis [N- ( 3-Acenaphthenyl) -N-phenyl-amino] biphenyl, 1,5-bis [N- (1-naphthyl) -N-phenyl-amino] naphthalene, 4,4′-bis [N- (9-anthryl)- N-phenyl-amino] biphenyl, 4,4 ″ -bis [N- (1-anthryl) -N-phenyl-amino] p-terphenyl, 4,4′-bis [N- (2-phenanthryl)- N-phenyl-amino] biphenyl, 4,4′-bis [N- (8-fluoranthenyl) -N-phenyl-amino] biphenyl, 4,4′-bis [N- (2-pyrenyl) -N— Phenyl-amino] biphenyl, 4 , 4′-bis [N- (2-perylenyl) -N-phenyl-amino] biphenyl, 4,4′-bis [N- (1-coronenyl) -N-phenyl-amino] biphenyl, 2,6-bis (Di-p-tolylamino) naphthalene, 2,6-bis [di- (1-naphthyl) amino] naphthalene, 2,6-bis [N- (1-naphthyl) -N- (2-naphthyl) amino] naphthalene 4.4 ″ -bis [N, N-di (2-naphthyl) amino] terphenyl, 4.4′-bis {N-phenyl-N- [4- (1-naphthyl) phenyl] amino} biphenyl 4,4′-bis [N-phenyl-N- (2-pyrenyl) -amino] biphenyl, 2,6-bis [N, N-di (2-naphthyl) amino] fluorene, 4,4 ″- Bis (N, N-di-p-tolylamino) terfeny , Bis (N-1-naphthyl) (N-2-naphthyl) amine.

Further, as the hole injection layer, the hole transport layer, and the hole transporting light emitting layer, those obtained by dispersing the above organic compound in a polymer or those polymerized can be used. So-called π-conjugated polymers such as polyparaphenylene vinylene and derivatives thereof, hole-transporting non-conjugated polymers typified by poly (N-vinylcarbazole), and sigma-conjugated polymers of polysilanes can also be used.

The hole injection layer is not particularly limited, but conductive polymers such as metal phthalocyanines such as copper phthalocyanine and metal-free phthalocyanines, carbon films, and polyaniline can be preferably used.

--- Metallate compounds having an electron-donating metal doped in the electron-transporting organic semiconductor layer as a counter cation--
Paying attention to the fact that the injection of electron holes from both electrodes of the organic EL element is an oxidation-reduction reaction that occurs at the interface with the organic organic semiconductor layer, an electron accepting property having an oxidizing action in the organic compound layer on the anode side. The compound is disposed, while the organic compound layer (electron injection layer) on the cathode side is doped with an electron-donating metal having a reducing action, but the doping form is fixed in the stoichiometric form of the metal salt compound. Thus, it is possible to reduce the energy barrier when electrons are injected from the cathode into the organic compound layer, and to suppress the diffusion of the electron donating metal into the organic compound layer under high temperature storage.

Since the electron-transporting organic semiconductor is already reduced by the electron-donating metal due to the metal salt compound having the electron-donating metal thus fixed as a counter cation, the electron injection energy barrier is small and the conventional organic semiconductor is reduced. The driving voltage can be reduced as compared with the EL element. In this case, the electron-donating metal is not particularly limited as long as it is an alkali metal such as Li, an alkaline earth metal such as Mg, or a transition metal containing a rare earth metal. In particular, a metal having a work function of 4.0 eV or less can be suitably used. Specific examples include Cs, Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, La, Mg, Sm, Gd, Yb, Etc.

The concentration of the metal salt compound in the electron transporting organic semiconductor layer is preferably 0.1 to 40% by weight. If it is less than 0.1% by weight, the concentration of the molecule reduced by the electron donating metal of the metal salt compound is too low, and the effect of doping is small. If it exceeds 40% by weight, the metal salt compound concentration in the film is organic. The concentration of semiconductor molecules is exceeded and the effect of doping is also reduced. The thickness of the electron transporting organic semiconductor layer is not particularly limited, but is preferably 1 nm to 300 nm. If the thickness is less than 1 nm, the amount of reducing molecules present in the vicinity of the electrode interface is small, so that the effect of doping is small. If the thickness exceeds 300 nm, the entire organic layer is too thick, leading to an increase in driving voltage.

It is preferable that at least the film of the electron transporting organic semiconductor layer is set to have a transmittance of 50% or more at the emission wavelength obtained from the organic light emitting material.

The film forming method of the electron transporting organic semiconductor layer 7 may be any thin film forming method. For example, a vapor deposition method or a sputtering method can be used. The electron transporting organic semiconductor layer is preferably formed by single vapor deposition or multiple vapor deposition. When a thin film can be formed by coating from a solution, a coating method from a solution such as a spin coating method or a dip coating method can be used. In this case, the organic compound to be doped and the dopant may be dispersed in an inert polymer.

The metal salt compound (Cs ₂ MoO ₄ etc.) in the present invention is a transition metal containing alkali metal, alkaline earth metal and rare earth metal having a work function of 4.0 eV or less (particularly preferably 3.5 eV or less) as the first component. And the like, and using a conductive metal oxide (MoOx, WOx, TiOx, SnOx, VxOy, ZnOx, ZrOx (x represents an atomic ratio), etc.) as the second component, the thermal stability is increased, and Since it is an oxide, its adhesion to the cathode (for example, Al, etc.) is increased and it becomes difficult to peel off.

By doping a metal acid salt compound into the organic semiconductor layer, the above problems can be solved and the device lifetime can be improved. Furthermore, the main component of such an organic semiconductor layer has a mobility (10 ⁻⁸ to 10 ¹ cm ² / Vs) or conductivity (10 ⁸ to 10 ⁻¹ Ω · cm) lower than that of an inorganic compound. Since the conductivity of the conductive metal oxide corresponding to the second component supplements the conductivity of the organic semiconductor layer, both the electron injection property and the electron transport property can be improved. Further, as mentioned above, since an electron injection layer of an inorganic compound is not required, the thickness can be reduced.

The conductive metal oxide as the second component preferably has a specific resistance of 10 ⁸ Ω · cm or less (MoO ₃ : 2.5 Ω · cm). In addition, since conductivity can be expressed by charge, carrier concentration, and mobility ((σ = neμ) conductivity is σ, e is an elementary charge, n is carrier concentration, μ is carrier mobility), the second component The conductive metal oxide is supplemented by carrier concentration or mobility. In particular, since the organic semiconductor material has a very low or no carrier concentration (10 ⁵ to 10 ¹⁰ cm ⁻³ ), the presence of the carrier concentration inside the thin film is very effective for improving electron transport properties. is there.

An electron transporting organic semiconductor layer (for example, Alq3) of a conventional element has an increased driving voltage as the film thickness increases. An electron transporting organic semiconductor layer doped with this metal salt compound in an electron transporting organic semiconductor layer. By using (a metal-inorganic-organic composite (composite) layer), an increase in driving voltage with respect to an increase in film thickness can be suppressed.

A plurality of organic EL devices each including a metal-inorganic-organic composite electron-transporting organic semiconductor layer comprising a metal acid salt compound having an electron-donating metal as a counter cation and an electron-transporting organic semiconductor were produced. The driving voltage and luminance with respect to the salt compound concentration, lifetime characteristics, and film thickness dependence characteristics of the electron transporting organic semiconductor layer were measured and evaluated.

As the metal salt compound, cesium molybdate Cs ₂ MoO ₄ and cesium tungstate Cs ₂ WO ₄ were used.

The electron transporting organic semiconductor EIL shown in Table 1 below was used as the electron transporting organic semiconductor.

Alq3: tris (8-hydroxy-quinolinato) aluminum

TPBI: 2,2 ', 2 "-(1,3,5-benzotritril) tris (1-phenyl) -1H-benzimidazole

NBphen: 2,9-bis (2-naphthyl) -4,7-diphenyl-1,10-phenanthroline

DBzA: 9,10-bis [4- (6-methylbenzothiazol-2-yl) phenyl] anthracene

Example 1
On the glass substrate on which the transparent electrode ITO was formed as an anode, copper phthalocyanine CuPc was formed in a thickness of 25 nm as a hole injection layer in order by vacuum deposition, and NPB: N, N ′ as a hole transport layer was formed thereon. -Bis (naphthalene-2-yl) -N, N'-diphenyl-benzidine was formed to a thickness of 45 nm. Further, a plurality of precursors formed in the same manner up to the hole transport layer are prepared, and Alq3 is formed as an organic light emitting layer on the hole transport layer with a thickness of 30 nm, and further, Cs ₂ MoO ₄ An electron transporting organic semiconductor layer made of Alq3 doped with a concentration of 0.85 wt%, 1.7 wt%, 3.3 wt%, 3.3 wt%, 5 wt%, 10 wt%, 20 wt%, and 40 wt% at a thickness of 30 nm by co-evaporation. Then, Al having a predetermined film thickness was formed thereon as a cathode by vacuum deposition. Thus, the organic EL element of Example 1 was produced.

Furthermore, on the hole transport layer of the precursor, Alq3 is formed as an organic light emitting layer with a thickness of 60 nm by vapor deposition, and Cs ₂ MoO ₄ is formed as an inorganic electron injection layer with a thickness of 1 nm thereon, On top of that, Al having a predetermined thickness was formed as a cathode by vacuum deposition. Thus, the organic EL element of the comparative example was produced. Similarly, a comparative organic EL device using Li ₂ O instead of the inorganic electron injection layer Cs ₂ MoO ₄ was also produced.

About the Example and the comparative example, each was driven on the conditions of current density 7.5mA / cm < ² >, and the drive voltage V and the brightness | luminance L were measured.

The experimental results are shown in Table 2 below.

As is clear from the results, it can be seen that the electron transporting organic semiconductor layer film of Cs ₂ MoO ₄ : Alq3 has a driving voltage lower than that of the comparative element at 10% concentration or more. If the light-emitting layer and the electron-transporting organic semiconductor layer are considered to be electron-transporting light-emitting layers, if the metal salt compound of the electron-donating metal counter cation is doped at a predetermined concentration from the contacting cathode side to the predetermined film thickness, It can be understood that the drive voltage can be reduced.

低減 Expected to extend the life of the device by reducing the drive voltage.

(Example 2)
In the same manner as in Example 1, a plurality of precursors formed up to the hole transport layer were prepared, and Alq3 was formed as an organic light emitting layer with a thickness of 30 nm on the hole transport layer. _{2 An} electron transporting organic semiconductor layer made of TPBI doped with MoO ₄ at a concentration of 5 wt%, 10 wt%, and 20 wt% is formed by co-evaporation to a thickness of 30 nm. It was formed by vapor deposition. Thus, the organic EL element of Example 2 was produced.

Furthermore, on the hole transport layer of the precursor, Alq3 is formed as an organic light emitting layer by vapor deposition by a thickness of 30 nm, and further, TPBI is formed as an electron transport layer by a thickness of 30 nm, and further, Li ₂ O was formed by vapor deposition as an inorganic electron injection layer with a thickness of 1 nm, and Al having a predetermined thickness was formed thereon as a cathode by vacuum vapor deposition. Thus, the organic EL element of the comparative example was produced.

The experimental results are shown in Table 3 below (a comparative example at the time of Example 1 is also shown).

As is clear from the results, it can be seen that the electron transporting organic semiconductor layer film of Cs ₂ MoO ₄ : TPBI has a driving voltage lower than that of the comparative element at 5% concentration or more. If the light-emitting layer and the electron-transporting organic semiconductor layer are considered to be electron-transporting light-emitting layers, if the metal salt compound of the electron-donating metal counter cation is doped at a predetermined concentration from the contacting cathode side to the predetermined film thickness, It can be understood that the drive voltage can be reduced.

低減 Expected to extend the life of the device by reducing the drive voltage.

(Example 3)
In the same manner as in Example 1, a plurality of precursors formed up to the hole transport layer were prepared, and Alq3 was formed as an organic light emitting layer with a thickness of 30 nm on the hole transport layer. _{2 An} electron transporting organic semiconductor layer composed of NBphen doped with MoO ₄ at a concentration of 1.7 wt%, 3.3 wt%, 5 wt%, 10 wt%, and 20 wt% is formed by co-evaporation to a thickness of 30 nm. As a cathode, Al having a predetermined thickness was formed by vacuum deposition. Thus, the organic EL element of Example 3 was produced.

The driving voltage V and the luminance L were measured by driving each of the examples under the condition of a current density of 7.5 mA / cm ² .

The experimental results are shown in the following Table 4 (a comparative example at the time of Example 1 is also shown).

As is clear from the results, it can be seen that the electron transporting organic semiconductor layer film of Cs ₂ MoO ₄ : NBphen has a concentration of 1.7% or more and a driving voltage lower than that of the comparative element. If the light-emitting layer and the electron-transporting organic semiconductor layer are considered to be electron-transporting light-emitting layers, if the metal salt compound of the electron-donating metal counter cation is doped at a predetermined concentration from the contacting cathode side to the predetermined film thickness, It can be understood that the drive voltage can be reduced.

低減 Expected to extend the life of the device by reducing the drive voltage.

Example 4
In the same manner as in Example 1, a plurality of precursors formed up to the hole transport layer were prepared, and Alq3 was formed as an organic light emitting layer with a thickness of 30 nm on the hole transport layer. _{2 An} electron transporting organic semiconductor layer made of DBzA doped with MoO ₄ at a concentration of 0.85 wt%, 1.7 wt%, 3.3 wt%, 5 wt%, 10 wt%, and 20 wt% is formed by co-evaporation to a thickness of 30 nm. On top of that, Al having a predetermined film thickness was formed as a cathode by vacuum deposition. Thus, the organic EL element of Example 4 was produced.

The experimental results are shown in Table 5 below (a comparative example at the time of Example 1 is also shown).

As is clear from the results, it can be seen that the electron transporting organic semiconductor layer film of Cs ₂ MoO ₄ : DBzA has a concentration of 3.3% or more and a driving voltage lower than that of the comparative element. The comparative element driving voltage is equivalent and effective even at a low concentration of 1.7%. If the light-emitting layer and the electron-transporting organic semiconductor layer are considered to be electron-transporting light-emitting layers, if the metal salt compound of the electron-donating metal counter cation is doped at a predetermined concentration from the contacting cathode side to the predetermined film thickness, It can be understood that the drive voltage can be reduced.

低減 Expected to extend the life of the device by reducing the drive voltage.

(Example 5)
For the electron transport materials Alq3, TPBI, NBphen, and DBzA devices of Examples 1 to 4, changes in driving voltage against the metal salt compound Cs ₂ MoO ₄ doping concentration were plotted. All the luminances were about 300 cd / m ² .

The result is shown in FIG. 9 (a comparative example at the time of Example 1 is also shown).

As is clear from FIG. 9, when the metal salt compound is doped in the organic semiconductor layer, a decrease in driving voltage is observed at a low concentration of about 1%, and it can be seen that the effect is obtained even at a low concentration.

On the other hand, even when a conventional electron injection material (such as CsF) is doped in the organic semiconductor layer, a decrease in driving voltage is observed. However, since the conventional electron injection material is insulative, the doping concentration is 20% or more. In particular, it has been found that a doping concentration of 30% or more is necessary even for Cs alone. The reason why a high doping concentration is necessary even for conductive Cs alone is that Cs ₂ O becomes cesium oxide during film formation by vacuum deposition because of the high alkali metal reactivity. it is conceivable that.

Usually, as the number of oxygen atoms in the metal oxide decreases, the energy gap becomes narrower. For example, MoO ₂ is less permeable than MoO ₃ . However, even if the organic semiconductor layer is doped, optical transmission loss is low because it exists as a single compound with the same number of oxygen atoms to exist in the state of a metal salt compound composed of this electron-donating metal pair cation. I can expect that.

The effect of doping the metal semiconductor compound into the organic semiconductor layer is also selective in the doped organic semiconductor layer. When the organic semiconductor layer has a deep HOMO level or a bond unit (phosphoric acid (P = O), carbonyl (C = O), boron, etc.), especially when an element with a high electronegativity of the unit is incorporated, the metal salt compound and the organic semiconductor material are newly added due to the charge bias (charge transfer complex). An impurity level is formed locally or mostly in the thin film, and the level is filled with the charge (carrier) of the metal salt, so that it can be expected that the electron transport property is improved. In addition, it can be expected to improve conductivity by forming and synthesizing a new compound by co-evaporation in a vacuum with a material having an unpaired electron such as a bathophenanthroline derivative such as NBphen.

Also, the higher the mobility of the organic semiconductor layer, the more effective the electron transport properties of the doping layer are.

(Example 6)
In the same manner as in Example 1, a plurality of precursors formed up to the hole transport layer were prepared, and Alq3 was formed as an organic light-emitting layer with a thickness of 30 nm on each of the hole transport layers. An electron transporting organic semiconductor layer made of NBphen doped with cesium acid Cs ₂ WO ₄ at a concentration of 1.7 wt%, 3.3 wt%, 5 wt% is formed by co-evaporation to a thickness of 30 nm, and a cathode is formed thereon. A predetermined thickness of Al was formed by vacuum deposition. Thus, the organic EL element of Example 6 was produced.

Further, Alq3 is formed as an organic light emitting layer with a thickness of 60 nm by vapor deposition on the hole transport layer of the precursor, and CsF is formed with a thickness of 1 nm as an inorganic electron injection layer thereon, and As a cathode, Al having a predetermined thickness was formed by vacuum deposition. Thus, an organic EL element of ITO / CuPc (25 nm) / NPB (45 nm) / Alq3 (60 nm) / CsF (1 nm) / Al as a comparative example was produced.

Example 6 and Comparative Example CsF were each driven at a current density of 7.5 mA / cm ² to measure drive voltage V and luminance L. For each element, metal salt compounds Cs ₂ WO ₄ and Cs ₂ MoO _The drive voltage change versus ₄ doping concentration was plotted. The results are shown in FIG. 10 (the plot of Example 3 is also shown).

From the above results, when a layer obtained by doping the metal salt compound Cs ₂ WO ₄ and Cs ₂ MoO ₄ in the organic semiconductor layer is used in the device, the concentration is lower than that of the conventional electron injection material (CsF). It can be seen that the doping has the effect of suppressing the luminance deterioration and greatly suppressing the increase of the driving voltage.

(Example 7)
The element of Example 3 (Cs ₂ MoO ₄ concentration 1.7 wt%) was driven for 100 hours or more under the condition of a current density of 21 mA / cm ² . The changes over time in the light emission intensity and the driving voltage in this case were plotted. The results are shown in FIGS. 11 and 12 (also driven in the same manner as using the electron injection layer Li 2 _O in the comparative example when the example 1, the results also are shown together).

As is apparent from FIGS. 11 and 12, when the element of Example 3, ie, the metal salt compound is doped in the organic semiconductor layer, the luminance deterioration (reduction) is small even at a low concentration of about 1%, and the driving voltage is reduced. It can be seen that there is little deterioration (rise). The reduction of the driving voltage is the same as the reduction of the power consumption, and the power consumption is proportional to the heat generation amount of the organic semiconductor layer as expressed in W (Watt). For this reason, the element whose voltage is lowered can suppress the generation of heat, and thus has an effect of not applying a load to the organic semiconductor layer.

(Example 8)
In the same manner as in Example 1, a plurality of precursors formed up to the hole transport layer were prepared, and Alq3 was formed as an organic light emitting layer with a thickness of 30 nm on the hole transport layer. _{2 An} electron transporting organic semiconductor layer made of NBphen doped with MoO ₄ at a concentration of 1.7 wt% is formed by co-evaporation to a thickness of 30 nm and 90 nm, and a predetermined thickness of Al is formed thereon as a cathode by vacuum evaporation. Formed. Thus, the organic EL element of Example 8 was produced.

The experimental results are shown in Table 6 below. Furthermore, the current density-voltage characteristic was measured and the change was plotted. The logarithmic graph and linear graph of the result are shown in FIGS.

As is clear from the above results, there is almost no difference in driving voltage with the film thickness even in the graph of current density-voltage characteristics in the examples, and there is no dependency on the film thickness of the metal salt compound-doped organic semiconductor layer. I understand.

(Example 7)
The device of Example 3 (Cs ₂ MoO ₄ concentration 1.7 wt%) and the device using the electron injection layer Li ₂ O of the comparative example in Example 1 were exposed to the atmosphere without using a desiccant. For more than 655 hours. Each result is shown in FIG.

As is apparent from FIG. 15, when the element of Example 3, ie, the metal salt compound is doped in the organic semiconductor layer, the effect of reducing the progress of the non-light emitting portion and the dark spot from the edge as compared with the comparative example element. I understand that there is.

In addition to the above examples, in addition to Cs ₂ MoO ₄ and Cs ₂ WO ₄ used in the examples, metal salt compounds include potassium molybdate K ₂ MoO ₄ , calcium molybdate CaMoO ₄ , and molybdic acid. Strontium SrMoO ₄ , sodium molybdate (anhydrous) Na ₂ MoO ₄ , barium molybdate BaMoO ₄ , lithium molybdate Li ₂ MoO ₄ , rubidium molybdate Rb ₂ MoO ₄ , calcium metastannate CaSnO ₃ , strontium metastannate SrO · SnO _2, meta tin barium BaSnO _3, metatitanic acid magnesium MgTiO _3,

metatitanic acid lithium

_Li 2 TiO _3, dichromate potassium _K 2 _Cr 2 _{O 7,} calcium chromate (n-hydrate) CaCrO ₄ · _nH 2 O, The Strontium romate SrCrO ₄ , cesium dichromate Cs ₂ Cr ₂ O ₇ , cesium chromate Cs ₂ CrO ₄ , potassium tungstate K ₂ WO ₄ , calcium tungstate CaWO ₄ , strontium tungstate SrWO ₄ , barium tungstate BaWO ₄ , Lithium tungstate Li ₂ WO ₄ , rubidium tungstate Rb ₂ WO ₄ , sodium tungstate Na ₂ WO ₄ , potassium divanadate K ₄ V ₂ O ₇ , sodium divanadate Na ₄ V ₂ O ₇ , potassium metavanadate KVO ₃ , potassium vanadate K ₃ VO ₄ , sodium metavanadate NaVO ₃ , sodium metavanadate NaVO ₃ , sodium vanadate Na ₃ VO ₄ , lithium metavanadate Li ₂ V ₂ O ₆ , rubidium metavanadate RbVO ₃ , cesium metavanadate Cs ₂ VO ₃ , potassium metatitanate K ₂ TiO ₃ , calcium metatitanate CaTiO ₃ , calcium metatitanate CaTiO ₃ , strontium metatitanate SrTiO ₃ sodium titanate ₂ Ti ₃ O ₇ , barium metatitanate BaTiO ₃ , and barium metatitanate BaTiO ₃ can be used to dope the organic semiconductor layer, and the same effects as in the above-described embodiment can be obtained.

Furthermore, although the organic EL element has been described as the organic semiconductor element in the above embodiment, in the organic solar cell in which the plurality of organic semiconductor layers include a light collection layer, and at least one of an electron transport layer and a hole transport layer, An electron composed of an organic semiconductor that is in contact with the interface of the organic semiconductor layer between the second electrode of the negative electrode and the adjacent organic semiconductor layer and is doped with the above metal salt compound having an electron donating metal as a counter cation. In the organic active light emitting device and the organic thin film transistor, the electron-donating metal is in contact with the interface of the organic semiconductor layer between the second electrode of the negative electrode and the adjacent organic semiconductor layer in the organic active light-emitting device or the organic thin film transistor. The structure having an electron-transporting organic semiconductor layer made of an organic semiconductor doped with a metal acid salt compound as described above having a counter cation as well as prolonging the life similar to the above examples Achieve the results and moisture effect.

Claims

An organic semiconductor element including a plurality of organic semiconductor layers stacked between a pair of opposing first and second electrodes, wherein the second electrode is a negative electrode, and the second electrode and the organic semiconductor layer An organic semiconductor comprising an electron-transporting organic semiconductor layer made of an organic semiconductor in contact with the interface of the organic semiconductor layer and doped with a metal salt compound having an electron-donating metal as a counter cation element.
The electron-donating metal is made of at least one metal selected from metals having a work function of 3.5 eV or less among transition metals including alkali metals, alkaline earth metals, and rare earth metals. 2. The organic semiconductor element according to 1.
3. The organic semiconductor element according to claim 1, wherein the concentration of the metal salt compound in the electron transporting organic semiconductor layer is 0.1 to 40% by weight.
The organic semiconductor element according to any one of claims 1 to 3, wherein a thickness of the electron transporting organic semiconductor layer is 1 nm to 300 nm.
The organic semiconductor element according to any one of claims 1 to 4, wherein the electron transporting organic semiconductor layer is formed by single vapor deposition or multiple vapor deposition.
6. The organic semiconductor element according to claim 1, wherein the film of the electron transporting organic semiconductor layer has a transmittance of 50% or more.
7. The organic semiconductor element according to claim 1, wherein the metal acid salt compound includes an oxide semiconductor having conductivity.
The oxide semiconductor having conductivity has carrier mobility of 1 × 10 −10 to 1 × 10 10 cm 2 / Vs, or conductivity of 10 10 to 10 −10 Ω · cm. 8. The organic semiconductor element according to 7.
9. The organic semiconductor element according to claim 1, wherein the organic semiconductor has a carrier mobility of 1 × 10 −10 to 1 × 10 10 cm 2 / Vs.
The organic electroluminescent element in which the plurality of organic semiconductor layers includes a light emitting layer, and one of the first and second electrodes is translucent or transparent, or the first and second electrodes are transparent. 10. The organic semiconductor element according to claim 1, wherein
The organic solar cell according to any one of claims 1 to 9, wherein the plurality of organic semiconductor layers are organic solar cells including a light collection layer and at least one of an electron transport layer and a hole transport layer. Organic semiconductor element.