Active solid-state devices (e.g. – transistors – solid-state diode – Organic semiconductor material
Patent
1994-03-15
1996-07-16
Crane, Sara W.
Active solid-state devices (e.g., transistors, solid-state diode
Organic semiconductor material
257103, 313504, 428690, H01L 3524, H01L 5100
Patent
active
055369499
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a novel charge injection auxiliary material and an organic electroluminescence device containing the same. More particularly, it pertains to a charge injection auxiliary material capable of enhancing charge injecting properties which comprises a derivative of stilbene, distyrylarylene or tris(styrylarylene) and an organic electroluminescence device having a lowered applied voltage, an enhanced light emission efficiency and a prolonged service life which contains the above-mentioned charge injection auxiliary material.
BACKGROUND ART
In recent years, it has been desired that an organic electronic device such an electrophotographic photoreceptor, an organic electroluminescence device (herein-after sometimes abbreviated to an "organic EL device"), organic transistor, an organic sensor and the like be capable of stably and efficiently injecting an electric charge from an electrode or charge generating layer to a charge transporting layer. Examples of such devices capable of stably and efficiently injecting an electric charge include a device comprising a positive-hole injecting layer having carbon black dispersed therein which layer is interposed between a type-P photoconductor layer and a supporting substrate (refer to Japanese Patent Application Laid-Open No. 12848/1984) and a device improved in charge injecting properties which comprises two divisional charge transporting layers, whose layer on the side of a charge generating layer is composed of a polymer layer having a distyryl compound dispersed therein (refer to Japanese Patent Application Laid-Open No. 157660/1991). However, the above-mentioned devices have been complicated in production because of the necessity of adding a new layer to the device.
In addition, there is disclosed an organic EL device technology which enhances a positive-hole injecting efficiency into an organic light-emitting layer by the use of a injecting layer comprising an aromatic tertiary amine (refer to Japanese Patent Application Laid-Open No. 295695/1988). Nevertheless the above-disclosed device does not fully satisfy electric power conversion efficiency and light-emitting efficiency. Thus, there is required an EL device capable of being driven by a lower voltage in order to enhance the power conversion efficiency and light-emitting efficiency of the device.
There is also disclosed an organic EL device technology which constitutes a light-emitting layer by mixing a styrylamine derivative being a positive-hole transporting material and also a light emitting material with an oxadiazole derivative being an electron transporting material (refer to Japanese Patent Application Laid-Open No. 250292/1990). However, the aforesaid technology relates to the incorporation of an oxadiazole derivative into a light emitting layer comprising a styrylamine to impart electron injecting properties to the layer, and discloses nothing about such function of a charge injection auxiliary material that improves charge injecting properties by adding a slight amount of a styrylamine to a light emitting layer (not being a styrylamine layer in most cases) or to an electron transporting layer.
There are known an EL device having an organic light-emitting layer in which 8-hydroxyquinoline aluminum complex as the host is doped with a slight amount of a fluorescent substance (refer to Japanese Patent Application Laid-Open No. 264692/1988) and an organic light-emitting layer in which 8-hydroxyquinoline aluminum complex as the host is doped with a quinacridone-based pigment (refer to Japanese Patent Application Laid-Open No. 255190/1991). Nevertheless, the above-mentioned dopants do not function as a charge injection auxiliary material.
DISCLOSURE OF THE INVENTION
Under such circumstances, intensive research and investigations were made by the present inventors in order to develop a charge injection auxiliary material capable of enhancing charge injecting properties by adding a slight amount thereof in a functional layer such as a light-emitting layer in
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Higashi Hisahiro
Hosokawa Chishio
Ikeda Kiyoshi
Kusumoto Tadashi
Crane Sara W.
Idemistu Kosan Co., Ltd.
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