Inverted OLED Stack with Alkali Metal Injection Layers
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Solution Overview
Problem
In light-emitting elements with an inverted stacked structure, it is challenging to select an anode material with high work function and reflectance or transmittance that can be stacked without damaging the element, leading to increased driving voltage and reduced emission efficiency.
Innovation Solution
A light-emitting element structure is proposed with a cathode, an anode, a light-emitting layer, and additional layers including alkali or alkaline earth metals and electron-transport materials, which helps in reducing the driving voltage and enhancing emission efficiency by optimizing the injection and transport of charge carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an anode material with high work function and high reflectance or transmittance is selected, then emission efficiency is improved, but it becomes difficult to stack without damaging the light-emitting element
Solution Approach 1:
An electron-injection layer comprising an alkali metal or alkaline earth metal is introduced as an intermediary between the anode and the light-emitting layer. This intermediary layer enables the use of anode materials with high work function and high reflectance or transmittance by facilitating electron injection while protecting the light-emitting element from damage during stacking.
2Reliability
If an anode material that can be stacked without damaging the element is used, then element integrity is maintained, but driving voltage increases and emission efficiency reduces
Solution Approach 1:
The electron-injection layer acts as a mediator that reconciles the conflict between element integrity and low driving voltage. It enables the anode to be stacked safely while maintaining appropriate electrical characteristics for low driving voltage operation.
Solution Approach 2:
The electron-injection layer changes the electrical parameters at the anode interface by providing appropriate work function matching and electron injection characteristics, thereby reducing driving voltage without compromising element integrity.
3Ease of manufacture
If an anode material with inappropriate work function is used, then stacking is easier, but emission efficiency reduces
Solution Approach 1:
The electron-injection layer serves as a universal intermediary that decouples the stacking process from the electrical performance requirements. Any anode material can be stacked easily, and the electron-injection layer ensures proper electron injection and emission efficiency.
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 structure achieves low driving voltage, high emission efficiency, and low power consumption while preventing damage to the light-emitting element, thereby improving the overall performance of the light-emitting device.
Implementation Method 1
By application of a voltage between the electrodes of this element, light emission from the light-emitting substance can be obtained
Implementation Method 2
the second layer includes a material having a function of transporting an electron
Data Source
AI summary
A light-emitting element includes a cathode, an anode, a light-emitting layer, a first layer, a second layer, and a third layer. The first layer is provided between the cathode and the light-emitting layer. The second layer is provided between the light-emitting layer and the third layer and includes a region in contact with the third layer. The third layer is provided between the second layer and the anode and includes a region in contact with the anode. The first layer and the third layer each include an alkali metal or an alkaline earth metal. The second layer includes a material that has a function of transporting an electron.