Organic electroluminescence device with oligomers

Details Organic electroluminescence device with oligomers Organic electroluminescence device with oligomers

1991-03-21

1992-08-25

Mintel, William

357 8, H01L 3300

Patent

active

051423430

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to an organic electroluminescence device, that is, it is concerned with organic EL device.
2. Background Art
As the above organic EL device, conventionally, there has been an EL device described in U.S. Pat. No. 3,995,299. Said organic EL device comprises anode/hole injection layer/polymer/electron injection layer/cathode, in which the concept of a hole injection layer has first been proposed. In this case, the representative example of a polymer as a light emitting layer is polyvinyl carbazol. The hole injection layer, which is formed by adding a high electron-accepting compound to said polymer, is an electroconducting layer in which cations exist. Said hole injection layer is capable of injecting holes to said polymer upon application of an electric field.
The electron injection layer, which is formed by adding a strong electron-donating compound, is an electroconducting layer in which anions exist. Said electron injection layer is capable of injecting electrons into said polymer upon application of an electric field.
Moreover, R. H. Partridge, Polymer, Vol. 24, page 748 (1983) discloses a hole injection layer and an electron injection layer in detail, and shows that these layers are capable of injecting electrons and holes into an organic insulator at low voltages.
However, in the above process, since a metal such as Ce, which is apt to be oxidized easily, is used as a strong electron-donating compound, stable light emission cannot always be obtained. Moreover, an oxidizing agent such as AlCl.sub.3 is used as an electron-accepting compound, and so stable light emission cannot be obtained because of a mobile ion such as AlCl.sub.3 .sup.- upon application of a higher voltage.
This type can be taken as one type of an MSISM (Metal Semiconductor Insulator Semiconductor Metal) type device.
Japanese Patent Publication 7635/1989 discloses a device comprising anode/hole injection zone/light emitting zone/cathode wherein a porphyrin compound is used in the hole injection zone and an organic luminescent substance having a binder polymer as a light emitting zone. This device was capable of showing a light emission of approximately 160 cd/m.sup.2 at an applied voltage of approximately 30 V and at a current density of approximately 100 mA/cm.sup.2. Moreover, holes were to be injected stably to the light emitting zone at a low voltage by using a porphyrin compound. However, in this device, the luminous efficiency is small at a high brightness of 50 cd/m.sup.2 or more, and the maximum was about 0.018 lm/W.
Japanese Patent Application Laid-Open 194393/1984 discloses a device comprising anode/hole injection zone/light emitting zone/cathode wherein a triphenylamine derivative is used for the hole injection zone. This device was capable of showing a light emission of approximately several hundred cd/m.sup.2 at an applied voltage of approximately 20 V and at a current density of approximately 100 mA/cm.sup.2. Said emission characteristics could attain to the area for practical use.
It has been known that the structure of charge generation layer/charge transport layer is used as a photoconductive material (for example, Electron Photograph Gakkaishi, Vol. 25, No. 3, pages 62 to 76), and the photo conductive device has also been known, in which holes are transported using the above triphenylamine derivative in a hole transport layer in said structure of charge generation layer/charge transport layer (for example, Japanese Patent Application Laid-Open Nos. 27033/1978 and 58445/1979, and U.S. Pat. No. 4,127,412).
It has also been known that holes are injected into said charge transport layer from an electrode and transported in the transport layer upon application of an electric field (for example, U.S. Pat. No. 4,251,621, and Japanese Patent Publication No. 824/1984).
The hole injection layer disclosed in the above specification of U.S. Pat. No. 3,995,299 is an electroconducting layer, while the triphenylamine derivative used for the above charge transport layer is a

REFERENCES:
patent: 4720432 (1988-01-01), Van Slyke et al.
patent: 4877852 (1989-10-01), Tanaka et al.
patent: 4939556 (1990-07-01), Eguchi et al.
Baughman et al., "The Structure of a Novel Polymeric Material: Acceptor-Doped Poylyaniline," Synthetic Metals, 25(1988), pp. 121-137.
Garnier et al., "Conjugated Poymers and Oligomers as Active Material for Electronic Devices," Synthetic Metals, 28(1989) pp. C705-C714, C729-C734.
Yokoyama, "Basic Probelms in Materials for Organic Photoreceptor," Electron Photograph Gaukaishi, vol. 25, No. 3, pp. 62-69.
Adachi et al., "Blue Light-Emitting Organic Electroluminescent Devices," Appl. Phys. Lett. 56(9), 26 Feb. 1990, pp. 799-801.

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