Auxiliary Electrode Oxidation for Uniform Luminance in Light-Emitting Devices
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Solution Overview
Problem
Light-emitting devices with organic compounds face issues of high manufacturing costs and non-uniform luminance due to the high resistivity of transparent conductive films and the need for complex processes to form auxiliary electrodes, leading to power loss and potential short circuits.
Innovation Solution
A light-emitting device structure incorporating an auxiliary electrode made of a low-resistivity metal, oxidized to form an insulating oxide layer, which is patterned using a shadow mask without photolithography, reducing capital investment and preventing power loss by covering the auxiliary electrode's surfaces, ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent conductive film is used as an electrode, then light transmission is achieved, but electrical resistivity is high leading to voltage drop and non-uniform luminance
Solution Approach 1:
The patent uses a composite electrode structure combining transparent conductive film and auxiliary electrode made of different materials (e.g., ITO and Alq3), leveraging the transparency of the first material and the low resistivity of the second material to achieve both light transmission and uniform electrical potential distribution
Solution Approach 2:
The auxiliary electrode acts as an intermediary between the transparent conductive film and the EL layer, providing a low-resistivity pathway for electrical current while the transparent conductive film maintains light transmission, thus mediating between optical and electrical requirements
2Reliability
If an auxiliary electrode is added to improve conductivity, then voltage drop is reduced, but manufacturing complexity increases due to additional steps and masks
Solution Approach 1:
The patent combines the auxiliary electrode formation with the existing shadow mask process used for EL layer deposition, integrating multiple functions into a single manufacturing step rather than adding separate processing steps
Solution Approach 2:
The shadow mask serves multiple functions: it defines the EL layer pattern, forms the auxiliary electrode pattern, and controls the oxidation process, eliminating the need for separate masks for each function
3Loss of energy
If an insulating layer is formed over the auxiliary electrode to prevent power loss, then emission extraction is blocked at overlapping portions, but manufacturing cost increases due to additional masks and alignment requirements
Solution Approach 1:
The auxiliary electrode material (e.g., Alq3) is chosen to form an oxide layer (Al2O3) with insulating properties when exposed to oxygen, allowing the material itself to provide the insulating function without requiring a separate insulating layer deposition process
Solution Approach 2:
The patent changes the chemical state of the auxiliary electrode material by controlled oxidation, transforming it from a conductive metal complex to an insulating oxide form, thereby providing electrical isolation without adding structural complexity
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 a light-emitting device with high reliability, reduced power loss, and uniform luminance, manufactured at a lower cost, suitable for large-area lighting applications.
Implementation Method 1
direct contact between the auxiliary electrode and an EL layer is prevented by oxidizing a surface of the auxiliary electrode
Data Source
AI summary
The manufacturing method of the light-emitting device is provided in which an auxiliary electrode in contact with an electrode formed using a transparent conductive film of a light-emitting element is formed using a mask, and direct contact between the auxiliary electrode and an EL layer is prevented by oxidizing the auxiliary electrode. Further, the light-emitting device manufactured according to the method and the lighting device including the light-emitting device are provided.