Organic EL Device Auxiliary Electrode Step Disconnection
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Solution Overview
Problem
In organic electroluminescence devices, step disconnection due to partition wall differences leads to light emission issues and display unevenness, particularly in top emission types where the transparent cathode is thinner than the partition walls, causing line disconnection and preventing satisfactory light emission.
Innovation Solution
The implementation of auxiliary electrodes thicker than the second electrode, which are continuously formed on the partition walls and within concave portions, ensuring electrical connection and preventing step disconnection, thereby maintaining sufficient current flow through the function layer for effective light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent cathode is formed as a thin film to guarantee light transmissive property, then light transmissive property is improved, but step disconnection occurs due to step difference with partition walls causing line disconnection
Solution Approach 1:
The cathode is segmented into two parts: a thin film transparent cathode for light transmission and a thick auxiliary cathode for reliable electrical connection. The thin film cathode (5-10 nm) is formed only in the concave portion where the organic electroluminescence element is located, while the auxiliary cathode is formed in the flat portion covering the partition wall top surface, thereby resolving the conflict between light transmission and electrical connectivity.
Solution Approach 2:
Different regions of the cathode structure are assigned different thicknesses and functions. The concave portion receives a thin transparent cathode optimized for light transmission, while the flat portion receives a thick auxiliary cathode optimized for electrical connection. This local differentiation allows each region to perform its specific function optimally without compromising the other.
2Illumination intensity
If the transparent cathode is formed in a thin film state, then light transmissive property is improved, but resistance value increases causing display unevenness
Solution Approach 1:
The cathode is divided into a thin film transparent cathode in the concave portion and a thick auxiliary cathode in the flat portion. The auxiliary cathode provides a low-resistance current supply path that compensates for the high resistance of the thin transparent cathode, thereby maintaining display uniformity while preserving light transmission properties.
Solution Approach 2:
The auxiliary cathode acts as an intermediary that supplies current to the thin transparent cathode. By placing the auxiliary cathode in the flat portion and connecting it to the function layer, it serves as a current reservoir that reduces voltage drop and ensures uniform brightness across the display area.
3Manufacturing precision
If partition walls are provided to improve location precision and prevent mixing of function liquid, then manufacturing precision is improved, but step difference causes line disconnection in thin film cathode
Solution Approach 1:
The cathode structure is segmented to accommodate the partition walls: the thin transparent cathode is formed only in the concave portion below the partition wall top surface, while the auxiliary cathode is formed in the flat portion covering the partition wall top surface. This segmentation allows the partition walls to provide their insulation function while the auxiliary cathode bridges the step difference to maintain electrical connectivity.
4Reliability
If auxiliary wire is added to reduce resistance value, then electrical connectivity is improved, but device complexity increases
Solution Approach 1:
The auxiliary cathode is merged with the transparent cathode to form an integrated cathode structure. Both are formed by the same vapor deposition process using the same cathode mask, creating a unified cathode system that provides both light transmission and low-resistance current supply without requiring separate auxiliary wire components.
Data Source
AI summary
An organic electroluminescence device includes an organic electroluminescence element having a function layer interposed between a first electrode and a second electrode. The function layer includes at least an organic light emission layer. The electroluminescence device includes: partition walls which define concave portions and each of formation areas of the organic electroluminescence element within each of the concave portions to arrange the function layer within the concave portion; and auxiliary electrodes which are each arranged continuously on the partition wall and within the concave portion. The second electrode is formed in an area where both the formation area of the organic electroluminescence element and a non-formation area of the organic electroluminescence element overlap with each other, so as to be electrically connected to the function layer and the auxiliary electrode and is formed continuously between the function layer arranged within the concave portion and the auxiliary electrode in a state where the second electrode contacts with the function layer arranged within the concave portion and the auxiliary electrode. The auxiliary electrode is formed to be thicker than the second electrode.