Auxiliary Electrode Protrusion for OLED Cathode Contact Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Top-emission type organic light emitting display devices face luminance non-uniformity issues due to voltage drop and contact failures between the cathode and auxiliary electrode, particularly in large-area displays, where the thin cathode increases electric resistance and misalignment during the formation process complicates the contact between the cathode and auxiliary electrode.
Innovation Solution
The organic light emitting display device incorporates an auxiliary electrode with a structural design that protrudes towards both sub-pixels from the corners of the partition, allowing stable contact with the cathode regardless of misalignment, and is formed on the same material as the anode, reducing the need for additional mask processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode is formed with a very thin thickness to acquire sufficient light transmittance, then light transmittance is improved, but electric resistance of the cathode increases
Solution Approach 1:
An auxiliary electrode is introduced as an intermediary component between the Vss voltage supply pad unit and the cathode. This auxiliary electrode provides an additional electrical conduction path, mediating the voltage supply to the cathode and compensating for the high resistance caused by the thin cathode structure, thereby resolving the contradiction between light transmittance and electric resistance
Solution Approach 2:
The solution transitions from a single-plane cathode structure to a multi-dimensional electrical conduction system by adding the auxiliary electrode that extends from the voltage supply pad unit to the cathode. This creates a three-dimensional electrical pathway that bypasses the resistance issue in the thin cathode while maintaining its optical properties
2Illumination intensity
If the cathode thickness is reduced to improve light transmittance, then light transmittance is improved, but voltage drop becomes more severe in large-area displays
Solution Approach 1:
The auxiliary electrode acts as a voltage compensation intermediary, providing an additional conduction path that reduces the voltage drop across the large-area display. By mediating the voltage supply through this intermediate structure, the system maintains adequate voltage potential despite the thin cathode design
Solution Approach 2:
The auxiliary electrode is pre-configured to extend from the voltage supply pad unit toward the cathode before final assembly, establishing a preliminary electrical pathway that proactively compensates for voltage drop issues before the device operates, thereby preventing energy loss in advance
3Reliability
If an auxiliary electrode is added to relieve voltage drop, then voltage uniformity is improved, but manufacturing complexity increases due to contact hole formation difficulties
Solution Approach 1:
The auxiliary electrode structure is merged with the existing partition structure, where the partition serves dual functions as both a physical separator and a support structure for the auxiliary electrode. This integration eliminates the need for separate contact hole formation processes, reducing manufacturing complexity while maintaining voltage uniformity
Solution Approach 2:
The partition structure is designed to serve multiple functions: it acts as a physical barrier between sub-pixels, provides mechanical support, and simultaneously serves as the substrate for the auxiliary electrode. This multi-functionality reduces the number of manufacturing steps while achieving the desired electrical uniformity
4Ease of manufacture
If the auxiliary electrode is formed on the planarization layer with the same material as the anode, then manufacturing process is simplified, but contact reliability between auxiliary electrode and cathode becomes problematic
Solution Approach 1:
The auxiliary electrode is designed with local quality variations, having different materials or structures in different regions. The portion contacting the cathode uses materials optimized for electrical contact, while other portions maintain consistency with the anode material for manufacturing simplicity, thereby resolving the contradiction between ease of manufacture and contact reliability
Data Source
AI summary
An organic light emitting display device comprises a substrate including a first sub pixel and a second sub pixel disposed in a first direction; a thin film transistor disposed on the substrate and corresponds to each of the first sub pixel and the second sub pixel; a planarization layer on the thin film transistor; an organic light emitting diode which is disposed on the planarization layer so as to correspond to each of the first sub pixel and the second sub pixel and has an anode, an organic emission layer, and a cathode; an auxiliary electrode between the first sub pixel and the second sub pixel; and a partition which is disposed on the auxiliary electrode so as to at least partially overlap the auxiliary electrode. The auxiliary electrode protrudes toward the first sub pixel and the second sub pixel from corners of the partition in plan view.