Organic EL Element Interlayer Structure for Electron Injection
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Solution Overview
Problem
Existing organic electroluminescence (EL) elements with inorganic barrier layers made of insulators, semiconductors, or metals with high work functions have low electron injection properties, leading to inadequate luminous performance and storage stability due to impurity degradation.
Innovation Solution
An organic EL element structure comprising a light-emitting layer, a first interlayer with a fluorine compound containing an alkali or alkaline-earth metal, and a second interlayer with a metal that cleaves the bond between the first metal and fluorine, where the thickness ratio of the second interlayer to the first interlayer is between 3% and 25%, ensuring effective impurity blocking and electron injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic barrier layers made of insulators, semiconductors, or metals with high work functions are used, then impurity blocking property is improved, but electron injection property deteriorates
Solution Approach 1:
The barrier layer is divided into two distinct layers: a first barrier layer made of an insulator with high impurity blocking property, and a second barrier layer made of a metal with high electron injection property. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between impurity blocking and electron injection properties.
Solution Approach 2:
Different regions of the barrier structure are assigned different material properties: the first barrier layer (closer to the light-emitting layer) uses insulating materials for superior impurity blocking, while the second barrier layer (closer to the electron injection layer) uses metallic materials for superior electron injection. This local differentiation of material quality optimizes both functions simultaneously.
2Reliability
If alkali metal or alkaline-earth metal functional layers are used, then electron injection property is improved, but storage stability deteriorates due to impurity degradation
Solution Approach 1:
The first barrier layer made of insulator acts as an intermediary between the light-emitting layer and the alkali metal/alkaline-earth metal functional layer. It provides a protective barrier that blocks impurities from reaching and degrading the reactive metal functional layer, thereby maintaining storage stability while allowing the metal layer to provide excellent electron injection properties.
Solution Approach 2:
The barrier structure combines insulating materials (for impurity blocking) with metallic materials (for electron injection) in a composite configuration. This composite approach allows the system to simultaneously achieve the complementary properties of both material types: the insulator protects against impurity degradation while the metal enables efficient electron injection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure enhances storage stability by blocking impurities and achieves superior luminous properties by ensuring sufficient electron injection to the light-emitting layer, balancing impurity blocking and electron supply properties.
Implementation Method 1
a second interlayer that is disposed on the first interlayer, and includes a second metal that has a property of cleaving a bond between the first metal and fluorine in the fluorine compound
Data Source
AI summary
An organic EL element includes: an anode; a light-emitting layer that is disposed above the anode; a first interlayer that is disposed on the light-emitting layer; a second interlayer that is disposed on the first interlayer; a functional layer that is disposed on the second interlayer; and a cathode that is disposed above the functional layer. The first interlayer includes a fluorine compound including a first metal that is an alkali metal or an alkaline-earth metal. The second interlayer includes a second metal that has a property of cleaving a bond between the first metal and fluorine in the fluorine compound. The functional layer has at least one of an electron transport property and an electron injection property. A thickness D1 of the first interlayer and a thickness D2 of the second interlayer satisfy 3%≤D2/D1≤25%.