OLED Cathode Resistance and Emission Efficiency via LiF:Yb Composite Layer
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Solution Overview
Problem
Organic light emitting display devices face challenges with high resistance in cathodes leading to voltage drops and reduced viewing angles, as well as complex deposition structures and reduced transmittance, which affect emission efficiency and lifetime.
Innovation Solution
An organic light emitting display device is designed with a composite electron injection layer (EIL) of LiF:Yb, which improves electron injection and transport, and an Ag monolayer cathode to reduce resistance, along with an optical correction layer to adjust resonance conditions for enhanced emission efficiency and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Mg:Ag is used as the cathode material, then the device can be manufactured with simple materials, but the high resistance causes voltage drop and reduced viewing angle
Solution Approach 1:
The patent uses a composite cathode structure consisting of LiF:Yb electron injection layer combined with Ag monolayer. This composite structure reduces the resistance and voltage drop while maintaining ease of manufacture, directly resolving the contradiction between simple material usage and voltage stability.
2Adaptability or versatility
If multiple stacked layers are used for microcavity structure, then color emission can be achieved, but the deposition structure and equipment become complicated
Solution Approach 1:
The patent combines the microcavity structure with the LiF:Yb electron injection layer, merging multiple functions into a single integrated structure. This reduces the number of separate deposition steps and equipment requirements while maintaining color emission capabilities through the inherent optical properties of the combined structure.
3Ease of manufacture
If Mg:Ag cathode is used, then manufacturing is simplified, but transmittance is reduced toward long wavelength requiring correction
Solution Approach 1:
The LiF:Yb composite layer is introduced to compensate for the wavelength-dependent transmittance reduction caused by Mg:Ag. This composite structure provides optical correction while maintaining manufacturing simplicity, as the LiF:Yb layer can be deposited in the same process as the cathode without requiring additional correction steps.
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 achieves improved driving characteristics, extended lifetime, and reduced voltage drops, while simplifying the manufacturing process by maintaining high current density and luminance with lower driving voltage, and enhancing color purity and efficiency.
Implementation Method 1
an electron injection layer (EIL) formed immediately on the emission structure layer and comprising a composite layer of LiF:Yb
Implementation Method 2
If the electrons and holes are recombined in some molecules, molecule excitons in an excited state of high energy are formed. The molecule excitons return to a ground state of low energy while emitting unique light of a material.
Data Source
AI summary
An organic light emitting display device includes a substrate; a first electrode layer formed on the substrate; an emission structure layer formed on the first electrode layer; an electron injection layer (EIL) formed immediately on the emission structure layer and comprising a composite layer of LiF:Yb; and a second electrode layer formed on the EIL.