JPH03289090A - Organic complex light emitting device - Google Patents

Abstract

PURPOSE:To obtain an EL device which emits light with good monochromaticity and has sufficient luminescence luminance and stability by using a thin film containing a rare earth metal organic complex in a positive hole transmissive organic compound as an electroluminescent layer. CONSTITUTION:A first electrode layer 2 of a transparent conductive thin film layer and a second electrode layer 5 of a metal electrode thin film layer are formed on a substrate, preferably a transparent substrate 1 of resin, glass, etc., and an electroluminescent layer 3 and an electron transmitting layer 4 are formed between these two electrode layers 2, 5. The electroluminescent layer 3 characterized the function of the EL device, that is the improvement of monochromaticity and light emitting efficiency of the device, and is composed of a thin film in which a positive hole transmissive organic compound and a rare earth metal organic complex are mixed. As the rare earth metal, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb are preferable. Consequently, an electroluminescent device with narrow width of luminescent spectrum and good monochromaticity and high conversion efficiency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electroluminescent (EL) device that performs charge injection, and more particularly to a light emitting device with excellent monochromaticity and high conversion efficiency.

[Background technology]

EL elements are generally classified into intrinsic type EL elements and injection type EL elements. Among these, the operation mechanism of injection type EL elements is as follows:
A forward bias is applied to a p-n junction such as a diode, electrons and holes are injected from both electrodes, and light is generated by their recombination. Generally this E
The L element has a structure in which a layer exhibiting the above-mentioned light-emitting function is placed between two electrodes, and is a light-emitting element that directly converts light energy into light by applying a voltage between these electrodes. The features of this device include its ability to operate in a wide drive frequency range from direct current to alternating current, low voltage drive, and high conversion efficiency from electricity to light. Unlike incandescent light bulbs and fluorescent lamps, it can be used for display materials such as lines, diagrams, images, etc. in various shapes such as thin-film panels, belt shapes, and cylindrical shapes, or planar light emitting materials such as large-area panels. It means having the possibility of realizing the body.

Conventionally, the material used for this injection type EL element is GaP.
Inorganic semiconductor materials have been mainly used. On the other hand, recently, an injection-type light emitting diode device with two layers of hole-conducting and electron-conducting organic compound thin films has been reported (C
, W, Tang: Appl, Phys, Lett,
, 5 12-(1987) 193), light-emitting elements using this organic material can freely change the color of the emitted light, can select from various thin film formation methods, and can form thin films over large areas with high precision. It is attracting attention because it has characteristics such as being possible.

However, in the reports such as those mentioned above, 8-hydroxyquinoline (AI) is mainly used for the purpose of obtaining green luminescence.
Ox)*) is used, and the center wavelength of its spectrum is 520n-, but its spectral width is 4B0
0, which is broad ranging from nm to 620rv+
In order to obtain monochromatic light with good color purity, a filter or the like must be used, which poses a problem when obtaining the three primary colors with good color purity and creating color display elements. As a solution to this problem, it has been difficult to obtain light emission with a narrow spectral width using organic materials that have been known so far. , is considered impossible in principle. Therefore, in order to solve this problem, there is a need for organic light-emitting materials and devices having characteristics such as a high one-emission transition probability, being less susceptible to environmental influences, and having a narrow emission spectrum width. Regarding this, the present inventors have
No. 1-217407 disclosed a light emitting device using an organic complex thin film.

The present inventors conducted further studies and found a light-emitting element with a narrow emission spectrum, excellent monochromaticity, and high conversion efficiency, which is proposed here.

[Disclosure of the invention]

That is, the present invention is a light emitting element in which a first electrode layer, a light emitting layer, an electron conductive layer, and a second electrode layer are formed in this order on a substrate, and the light emitting layer is made of a hole conductive organic compound and a rare earth metal. This is a light-emitting device characterized by being made of a thin film mixed with an organic complex.

FIG. 1 shows one embodiment thereof. Substrate, preferably a transparent substrate such as resin or glass 1. A first electrode layer 2 consisting of a transparent conductive thin film layer and a second electrode layer 5 consisting of a metal electrode thin film layer are provided, and these two electrodes 2.5
This is a light emitting element in which a light emitting layer 3 and an electron conductive layer 5 are provided between the layers.

The light-emitting layer in the present invention is characterized by improved EL performance, that is, monochromaticity and luminous efficiency. The important point is to become more

The organic complexes of rare earth metals will be explained below.

Rare earth metals include yttrium (Y) and lanthanum (
La), cerium (Ce), praseodymium (Pr
), neodymium (Nd), promethium (Pa),
Samarium (Sad).

Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Ts)
, ytterbium (Yb), and lutetium (Lu), among them cerium (Ce) and praseodymium (P).
r), neodymium (Nd), promethium (Pa), samarium (Ss), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (), erbium (Er), thulium (T) .

Divalent, trivalent or tetravalent ions of these metals are used, preferably ytterbium (Yb).

In addition, as organic ligands, those having a β-diketone group such as acetylacetone, dibenzoylmethane, and 2-thenoyl trifluoroacetone; carboxylic acids such as 0-benzoylbenzoic acid, salicylic acid, and 0-phthalic acid. Those with a ketone group or aldehyde group adjacent to the hydroxyl group of salicylaldehyde, 0-hydroxyacetophenone, and 0-hydroxybenzophenone; Oxine I! such as 8-hydroxyquinoline and 5,7-dibromooxine! , 2.2°-bipyridine, 2.2"12"' tripyridine, pyridines such as L 10-phenanthroline, and crown ethers, and these ligands may be used alone or in combination.

On the other hand, organic conductive (hole conductive) organic compounds include amine-based organic compounds, polyvinyl carbazole,
Conductive polymer compounds such as polypyrrole and polythiophene are used.

The light-emitting layer in the present invention is a thin film containing a mixture of the hole-conducting organic compound and a rare earth metal organic complex.The concentration of the organic complex in the light-emitting layer is not particularly specified, but is usually 0. .01-20mo1% or 0.
It is about 01 to 10 wt%.

The thin film containing the metal complex described above is used in the form of amorphous, microcrystalline, amorphous including microcrystalline, polycrystalline, and single crystal "f31M".The thickness of the thin film is not particularly limited. , usually about 50 to 5,000 people are employed.Of course, it is possible to use a range outside this range.

The thin film can be formed by various physical or chemical thin film forming methods such as vacuum evaporation, and sublimation, coating, and the like can also be effectively used.

In the present invention, as the electron conductive layer, an inorganic semiconductor thin film, an oxadiazole organic compound thin film, a metal complex thin film such as aluminum oxine, etc. can be used. The inorganic semiconductor thin film may be one type of inorganic semiconductor thin film or a laminated film of two or more types of inorganic semiconductor thin films. These are amorphous thin film, microcrystalline thin film, polycrystalline thin film,
A single crystal thin film, a thin film in which amorphous and microcrystalline materials are mixed, a laminated thin film of these thin films, an artificial lattice thin film, etc. are used. Inorganic semiconductor materials useful for forming these thin films include C, G
Single-component semiconductors such as e, Si, and Sn, binary IV-TV group semiconductors such as SiC, AlSb BN BP
, GaN, GaSb, GaAs.

■-■ such as GaP InSb InAs, InP
Group semiconductors, CdS, CdSe, CdTe, ZnOZnS
, n-Vl group semiconductor materials such as Zn5e, and multi-component compound semiconductor materials. To give a specific example of Si (silicon), which is a preferable material,
Amorphous silicon (a-5i), hydrogenated amorphous silicon (
a-5i:)I), microcrystalline silicon (μc-3t),
Polycrystalline silicon, single crystal silicon, hydrogenated amorphous silicon carbide (!l++ +-X Cx:H), microcrystalline silicon carbide (μc-3iC), single crystal silicon carbide, amorphous silicon nitride, hydrogenated non- Crystalline silicon nitride, microcrystalline silicon nitride, etc. are preferably used. Here, the above-mentioned inorganic semiconductor thin film is used as an n-type film by doping or the like so that the thin film itself has hole conductivity. Note that the thickness is not particularly limited, but usually about 10 to 3000 people are used. Of course, other materials can also be used. The method for producing the above inorganic semiconductor thin film includes photo-CVD method, plasma CVD method,
method, thermal CVD method, molecular beam epitaxy (M
BE) method, metal organic decomposition method (MOCVD).

Various physical or chemical thin film forming methods such as vapor deposition and sputtering are used.

As the two electrode layers in the present invention, metal alloys, metal oxides, metal silicides, etc., or laminated thin films of one or more types thereof are used. More preferably, a material with high injection efficiency of electrons or holes into the thin film in contact is selected. For example, regarding a device formed in the following order: a first electrode layer, a light emitting layer made of an organic thin film containing a rare earth metal complex in polyvinylcarbazole, an electron conductive layer made of an oxadiazole thin film, and a second electrode layer. This will be explained using an example.

For the first electrode layer, it is preferable to use an electrode material with high hole injection efficiency into the light emitting layer, which is made of an organic thin film containing a rare earth metal complex in polyvinyl carbazole. To be more specific, the electrode materials generally include metals with large electron work functions, alloys, metal compound thin films such as metal oxides, conductive polymer materials, and laminated thin films of these materials. . Furthermore, the light generated from this first electrode can also be extracted. For this purpose, the first electrode is preferably formed of a transparent or semitransparent material. Specifically, thin films of metal oxides such as tin oxide (SnO□), indium oxide, and indium-tin oxide (ITO), or laminated films thereof, PL, ^u, Se, Pd,
Preferred examples include thin films of metals or alloys such as Ni, W, Ta, Te, etc., laminated films thereof, metal salt* films such as Cul, and laminated films thereof.

Since the second electrode layer injects electrons into the oxadiazole-based thin film, it generally includes a metal or alloy thin film with a small electron work function, a laminated thin film thereof, or the like. More specifically, Mg, Li, Na, Ca, Rh,
Alkali metals such as Sr and Ce, alkaline earth metals,
Rare earth elements, alloys such as Mg-Ag, CCs-0-A,
Cs5sb, NazKSb, (Cs)NazKS
Thin films such as b, etc., and laminated thin films thereof are suitable.

Note that the thickness of the electrode layer is not particularly limited, but is usually about 1,000 to 10,000.

The device of the present invention can be suitably used as a member for color display by arranging light-emitting devices of the three primary colors of blue, green, and red in a segment shape in a plane.

〔Example〕

An ITO film with a thickness of 5000 was formed on a glass substrate to serve as a first electrode layer. Terbium acetylacetonate (T
b (ac a c) i) containing 1-01% of polyvinyl carbazole! A thin film with a thickness of 1000 mm was formed to serve as a light emitting layer. Furthermore, on this layer, (2-4-(Biphenyl)-5-
(4-tert-butyl phenyl)-1-3
An organic thin film of -4-oxadiazol was formed by 400 people to serve as an electron conductive layer. Further, an AI metal thin film was deposited to form a second electrode layer, thereby obtaining a light emitting device of the present invention as shown in FIG. Note that the area of the AI gold metal vapor deposited film is 1 cm square. When a DC voltage was applied to this light emitting element, 10
At voltages above V, bright green luminescence was observed that could be seen under indoor fluorescent lighting. The main emission wavelength at this time is 545 nm,
The spectral width at this wavelength was about 10 nm, and it exhibited very excellent monochromatic properties. Figure 2 shows the measurement results of the emission spectrum. Furthermore, the quantum conversion efficiency from emitted electrons to photons was 2.2χ.

〔Effect of the invention〕

The present invention provides an injection-type EL device that operates by injecting electrons from one electrode and holes from the other electrode, in which a light-emitting layer contains an organic complex of a rare earth metal in a hole-conducting organic compound. By using a thin film, an EL element with excellent monochromatic light emission and sufficient luminance and stability can be achieved. As is clear from the examples, the injection type light emitting device of the present invention is a high performance light emitting device that could not be achieved using conventional technology, and is extremely useful industrially as a color Table 2 display member, etc. It is something.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of implementation of the light emitting device of the present invention. In the figure, 1-m-----substrate such as a glass plate, 2-----
-------1st electrode layer consisting of a transparent conductive film, etc., 3--
-1.- A light-emitting layer consisting of a thin film containing an m-complex of a rare earth metal in a hole-conducting organic compound, 4--1 to ---
---An electron conductive layer consisting of an electron conductive organic thin film,
5-----A second electrode layer made of an AI metal thin film or the like. FIG. 2 is an explanatory diagram showing an example of the emission spectrum of the element of the present invention. In the figure, the vertical axis shows the relative emission intensity, and the horizontal axis shows the wavelength. Figure 1

Claims (1)

[Claims] (1) A light-emitting element in which a first electrode layer, a light-emitting layer, an electron-conducting layer, and a second electrode layer are formed in this order on a substrate, and the light-emitting layer is an organic complex of a hole-conducting organic compound and a rare earth metal. 1. A light emitting device comprising a thin film containing a mixture of.