Oxide Layer Oxygen Density Gradient for Light-Emitting Element Injection Barriers
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Solution Overview
Problem
Existing light-emitting elements, such as OLEDs and QLEDs, face challenges with poor luminous efficiency due to difficulties in efficiently injecting holes and electrons into the light-emitting layer, primarily attributed to high injection barriers.
Innovation Solution
A light-emitting element configuration that includes an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode, with additional first and second oxide layers inserted between the hole transport layer and the light-emitting layer or between the light-emitting layer and the electron transport layer. The oxide layers have different oxygen atom densities, facilitating the formation of electric dipoles that reduce the hole and electron injection barriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials for hole transport layer, electron transport layer, and light-emitting layer are selected from limited materials with long-term reliability, then device reliability is improved, but injection barrier height increases and luminous efficiency deteriorates
Solution Approach 1:
The patent introduces an oxide layer as an intermediary between the hole transport layer and the light-emitting layer. This oxide layer contains oxygen vacancies that act as mediator states, facilitating carrier injection by bridging the energy gap between the transport layer and light-emitting layer, thereby reducing the injection barrier while maintaining material reliability.
Solution Approach 2:
The patent changes the oxygen content parameter in the oxide layer by controlling oxygen partial pressure during formation. By adjusting the oxygen vacancies concentration, the energy level alignment between layers is optimized, reducing the injection barrier height without compromising the long-term reliability of the constituent materials.
2Ease of operation
If band level of light-emitting layer is adjusted by forming organic ligand distribution with different surfaces, then turn-on voltage and drive voltage are reduced, but the reduction in injection barrier height is insufficient
Solution Approach 1:
The oxide layer serves as a mediator that provides intermediate energy states through oxygen vacancies. This enables more effective band level alignment between the hole transport layer and light-emitting layer, achieving greater reduction in injection barrier height compared to organic ligand distribution alone.
Solution Approach 2:
The patent changes the energy level parameter of the interface by controlling the oxygen vacancies concentration in the oxide layer. This provides a more effective mechanism for adjusting band alignment and reducing injection barriers compared to organic ligand modifications.
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
This configuration enhances the luminous efficiency of the light-emitting element by reducing the height of the hole and electron injection barriers, allowing for more efficient carrier injection into the light-emitting layer.
Implementation Method 1
The oxide layers have different oxygen atom densities, facilitating the formation of electric dipoles that reduce the hole and electron injection barriers
Data Source
AI summary
A light-emitting element includes: a first electrode which is an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a second electrode which is a cathode in this order; and an oxide layer which is a first oxide layer and an oxide layer which is a second oxide layer disposed in this order from the first electrode side between the hole transport layer and the light-emitting layer or between the light-emitting layer and the electron transport layer, wherein a density of oxygen atoms in the second oxide layer is different from a density of oxygen atoms in the first oxide layer.