Organic EL Electron Injection Layer with d0 Metal Oxide
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Solution Overview
Problem
Conventional organic electroluminescent elements with titanium oxide electron injection layers suffer from low transmittance, reduced luminous efficiency, and inhibited electron injection due to oxygen defects, making them unsuitable for top-emission applications and requiring high electron injection barriers.
Innovation Solution
An organic electroluminescent element with an electron injection layer containing a metal oxide with d0 electron configuration, where the Fermi level is near the lower end of the conduction band, minimizing oxygen defects and enhancing electron conduction and injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium oxide with many oxygen defects is used as electron injection layer, then electron conduction is improved, but transmittance decreases and luminous efficiency is reduced
Solution Approach 1:
The patent changes the oxygen content parameter in titanium oxide from high (many defects) to low (few defects), and adjusts the Fermi level position from deep in the band gap to near the conduction band edge. This parameter optimization achieves both good electron conduction and high transmittance, resolving the contradiction between reliability and illumination intensity
Solution Approach 2:
The patent creates a specific local electronic structure quality in the titanium oxide layer by positioning the Fermi level near the conduction band and controlling oxygen defect density. This localized electronic structure optimization enables simultaneous achievement of electron conduction and optical transparency
2Ease of manufacture
If conventional electron injection layer is used, then manufacturing is simplified, but air stability of functional layer deteriorates
Solution Approach 1:
The titanium oxide layer acts as an intermediary between the cathode and the organic functional layer. It provides a stable interface that protects the functional layer from air degradation while maintaining good electron injection properties. The layer's stability to oxygen and water makes it an effective mediator that preserves functional layer integrity
3Stability of the object's composition
If sealed structure is used to protect from air, then air stability is improved, but device complexity increases
Solution Approach 1:
The stable titanium oxide electron injection layer serves as an intermediary protective interface that reduces the need for complex sealing structures. By providing inherent stability to oxygen and water at the critical electrode-functional layer interface, it simplifies the overall device protection requirements while maintaining air stability
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 solution results in an organic electroluminescent element with improved air stability, high transmittance, efficient electron injection, and low power consumption, enabling longevity and efficient light emission across a broad range of luminance levels.
Implementation Method 1
electrons are assumed to be injected from a Fermi level of the cathode into a lower end of a conduction band of titanium oxide, conduct the lower end of the conduction band, and are injected into the LUMO
Implementation Method 2
use the phenomenon of electroluminescence that occurs when holes injected from the anode into the functional layer recombine with electrons injected from the cathode into the functional layer
Data Source
AI summary
An organic EL element including: an anode and a cathode disposed to face each other with a gap therebetween; a functional layer that contains an organic material and is disposed between the anode and the cathode; and an electron injection layer that has a function to inject electrons into the functional layer and is disposed between the anode and the cathode. The electron injection layer contains a metal oxide with d0 electron configuration, and a Fermi level of the electron injection layer is located in a vicinity of a lower end of a conduction band of the electron injection layer.