OLED Barrier Layer for Black Spot Reduction
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Solution Overview
Problem
Conventional organic light emitting diode (OLED) displays face issues with light efficiency and black spot generation due to the thickness limitations of organic emission layers, which are prone to defects from sub-micrometer particles on the surface of light-reflective electrodes.
Innovation Solution
An organic light emitting element is designed with a first electrode having a light-reflective sub-electrode and a transparent conductive sub-electrode, along with a barrier layer made of a lanthanide or transition metal oxide, which reduces metal particle ejection and improves hole injection characteristics, enhancing light efficiency and minimizing black spot formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the thickness of the organic emission layer is reduced to suit the wavelength of emitted light, then light efficiency is improved, but black spots and cell defects occur due to sub-micrometer particles on the electrode surface
Solution Approach 1:
A barrier layer made of metal oxide (such as indium oxide, tin oxide, zinc oxide, gallium oxide, or silicon oxide) is introduced as an intermediary between the light-reflective electrode and the organic emission layer. This barrier layer prevents direct contact between sub-micrometer particles on the electrode surface and the organic emission layer, thereby eliminating black spots while allowing the organic emission layer to maintain its optimized thin thickness for high light efficiency
Solution Approach 2:
The electrode structure is designed as a composite system comprising a light-reflective electrode, a metal oxide barrier layer, and the organic emission layer. This composite structure combines the light-reflective properties of the electrode with the protective and transparent characteristics of the metal oxide barrier layer, achieving both high light efficiency and reliability
2Use of energy by moving object
If a light-reflective first electrode is used in top emission display, then light efficiency is improved, but sub-micrometer particles on the surface cause defects
Solution Approach 1:
The metal oxide barrier layer serves as a protective intermediary that filters out sub-micrometer particles from reaching the organic emission layer while maintaining optical transparency. This allows the light-reflective electrode to function effectively without being compromised by surface particles
Solution Approach 2:
The barrier layer is specifically positioned at the interface where particle contamination is most problematic, providing localized protection exactly where needed. The layer has different properties than the electrode itself - it is transparent and protective rather than highly reflective, creating local quality differentiation to solve the specific problem of particle-induced defects
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 effectively improves light efficiency and reduces black spot generation by maintaining a consistent barrier layer thickness and utilizing a second metal oxide with a high work function, enhancing transmittance and hole injection characteristics.
Implementation Method 1
the second metal may be a lanthanide metal or a transition metal having a work function that is larger than that of the first metal. The work function of the barrier layer may be equal to or greater than about 5.40 eV.
Implementation Method 2
the first electrode is light reflective and the second electrode is semi-transmissive. The microcavity structure serves to improve the light efficiency (e.g., light emitting efficiency) of each red, green, or blue light
Implementation Method 3
The organic light emitting diode of the top emission display has a structure in which the first electrode is light reflective and the second electrode is semi-transmissive. Such a top emission organic light emitting diode display has a microcavity structure.
Data Source
AI summary
According to an exemplary embodiment of the present disclosure, an organic light emitting element includes: a first electrode; an organic emission layer disposed on the first electrode; and a second electrode disposed on the organic emission layer. The first electrode includes a first sub-electrode including a first metal, a second sub-electrode disposed on the first sub-electrode and including a transparent conductive material, and a barrier layer disposed on the second sub-electrode and including a second metal in the form of an oxide.