Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1999-01-21
2001-08-28
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S498000, C313S503000, C313S504000, C313S509000, C428S690000, C428S917000
Reexamination Certificate
active
06281627
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to an organic electroluminescent (EL) device and more particularly, to an inorganic/organic junction structure suitable for use in a device of the type wherein an electric field is applied to a thin film of an organic compound to emit light.
2. Background Art
Research and development efforts have been made on organic EL devices for display applications because the devices can be formed on glass over a substantial area. In general, organic EL devices have a basic configuration including a glass substrate, a transparent electrode of ITO etc., a hole transporting layer of an organic amine compound, an organic light emitting layer of a material exhibiting electronic conductivity and intense light emission such as Alq3, and an electrode of a low work function metal such as MgAg, wherein the layers are stacked on the substrate in the described order.
The device configurations which have been reported thus far have one or more organic compound layers interposed between a hole injecting electrode and an electron injecting electrode. The organic compound layers are typically of two- or three-layer structure.
Included in the two-layer structure are a structure having a hole transporting layer and a light emitting layer formed between the hole injecting electrode and the electron injecting electrode and another structure having a light emitting layer and an electron transporting layer formed between the hole injecting electrode and the electron injecting electrode. Included in the three-layer structure is a structure having a hole transporting layer, a light emitting layer, and an electron transporting layer formed between the hole injecting electrode and the electron injecting electrode. Also known is a one-layer structure wherein a single layer playing all the roles is formed from a polymer or a mixed system.
FIGS. 3 and 4
illustrate typical configurations of organic EL devices.
In
FIG. 3
, a hole transporting layer
14
and a light emitting layer
15
of organic compounds are formed between a hole injecting electrode
12
and an electron injecting electrode
13
on a substrate
11
. In this configuration, the light emitting layer
15
also serves as an electron transporting layer.
In
FIG. 4
, a hole transporting layer
14
, a light emitting layer
15
, and an electron transporting layer
16
of organic compounds are formed between a hole injecting electrode
12
and an electron injecting electrode
13
on a substrate
11
.
Attempts have been made to improve the luminous efficiency of these organic EL devices. With the prior art device configuration, however, for reasons of poor electron injection efficiency of the electron injecting and transporting layer, it was difficult to achieve effective recombination in the light emitting layer and hence, to provide a device with a fully satisfactory efficiency.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an organic EL device having an excellent electron injection efficiency, improved luminous efficiency, low operating voltage, and low cost.
This and other objects are achieved by the present invention which is defined below.
1. An organic electroluminescent device comprising
a hole injecting electrode,
an electron injecting electrode,
at least one organic layer between the electrodes, at least one layer of said organic layer having a light emitting function, and
a high resistance inorganic electron injecting layer between said electron injecting electrode and said light emitting layer, said high resistance inorganic electron injecting layer comprising as a first component an oxide of at least one element selected from alkali metal elements, alkaline earth metal elements and lanthanide elements, having a work function of up to 4 eV and as a second component at least one metal having a work function of 3 to 5 eV, and said high resistance inorganic electron injecting layer being capable of blocking holes and having conduction paths for carrying electrons.
2. The organic electroluminescent device of (1) wherein said second component is at least one metal selected from the group consisting of Zn, Sn, V, Ru, Sm, and In.
3. The organic electroluminescent device of (1) wherein said alkali metal elements include Li, Na, K, Rb, Cs, and Fr, said alkaline earth metal elements include Mg, Ca, and Sr, and said lanthanide element include La and Ce.
4. The organic electroluminescent device of (1) wherein said high resistance inorganic electron injecting layer has a resistivity of 1 to 1×10
11
&OHgr;-cm.
5. The organic electroluminescent device of (1) wherein said high resistance inorganic electron injecting layer contains 0.2 to 40 mol % based on the entire components of the second component.
6. The organic electroluminescent device of (1) wherein said high resistance inorganic electron injecting layer has a thickness of 0.3 to 30 nm.
7. The organic electroluminescent device of (1) further comprising a high resistance inorganic hole injecting layer between said hole injecting electrode and said organic layer, said high resistance inorganic hole injecting layer being capable of blocking electrons and having conduction paths for carrying holes.
8. The organic electroluminescent device of (7) wherein said high resistance inorganic hole injecting layer has a resistivity of 1 to 1×10
11
&OHgr;-cm.
9. The organic electroluminescent device of (7) wherein said high resistance inorganic hole injecting layer contains an insulative metal or metalloid and at least one member selected from the group consisting of oxides, carbides, nitrides, silicides and borides of metals.
10. The organic electroluminescent device of (7) wherein said high resistance inorganic hole injecting layer contains
silicon oxide or germanium oxide or a mixture of silicon oxide and germanium oxide as a main component, the main component being represented by the formula: (Si
1-x
Ge
x
)O
y
wherein 0≦x≦1 and 1.7≦y≦2.2, and
a metal having a work function of at least 4.5 eV or an oxide thereof.
11. The organic electroluminescent device of (7) wherein said metal having a work function of at least 4.5 eV is at least one member selected from the group consisting of Au, Cu, Fe, Ni, Ru, Sn, Cr, Ir, Nb, Pt W, Mo, Ta, Pd, and Co.
12. The organic electroluminescent device of (10) wherein the content of said metal and/or metal oxide is 0.2 to 40 mol %.
13. The organic electroluminescent device of (7) wherein said high resistance inorganic hole injecting layer has a thickness of 1 to 100 nm.
REFERENCES:
patent: 5853905 (1998-12-01), So et al.
patent: 5952779 (1999-09-01), Arai et al.
patent: 5969474 (1999-10-01), Arai
patent: 5981092 (1999-11-01), Arai et al.
patent: 196 25 993 (1998-01-01), None
patent: 0 740 489 (1996-10-01), None
patent: 9-260062 (1997-10-01), None
patent: 11-111461 (1999-04-01), None
patent: WO 98/10473 (1998-03-01), None
Arai Michio
Kobori Isamu
Mitsuhashi Etsuo
Yamamoto Hiroshi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Vip
Quarterman Kevin
TDK Corporation
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