Auxiliary Electrode Segmentation for OLED Brightness Uniformity
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Solution Overview
Problem
Large-sized organic light emitting display devices face issues with non-uniform brightness due to voltage drops caused by cathode electrode resistance, leading to brightness differences between peripheral and central areas, and existing solutions like auxiliary electrodes face challenges in contact and leakage current suppression.
Innovation Solution
An organic light emitting display device design featuring a substrate with a first electrode, an auxiliary electrode, a bank pattern, and a barrier rib with specific shapes to facilitate contact between the cathode and auxiliary electrodes, reducing voltage drops and leakage currents, and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an auxiliary electrode is introduced to solve voltage drop, then brightness uniformity is improved, but contact between cathode electrode and auxiliary electrode becomes difficult and leakage current may be generated
Solution Approach 1:
The auxiliary electrode is segmented into multiple regions: a first region where the organic emission layer is not disposed, allowing direct contact with the cathode electrode, and a second region where the organic emission layer is disposed. This segmentation enables the auxiliary electrode to simultaneously achieve contact with the cathode electrode (reducing voltage drop) and function as an emission electrode (improving brightness uniformity) without causing leakage current.
2Area of stationary object
If the OLED device is manufactured to a large size, then display area is increased, but brightness uniformity between peripheral and central areas deteriorates due to voltage drop
Solution Approach 1:
The auxiliary electrode is configured to be electrically connected to the cathode electrode through a contact region, creating an equipotential structure. This connection compensates for voltage drops in large-sized devices by providing an additional current injection point, thereby maintaining uniform brightness across the entire display area including both peripheral and central regions.
3Illumination intensity
If organic material is formed to a large thickness on the auxiliary electrode, then emission performance is improved, but leakage current is generated
Solution Approach 1:
The auxiliary electrode surface is divided into a first region without organic emission layer (preventing leakage current) and a second region with organic emission layer (providing emission performance). This spatial segmentation allows the device to achieve good emission performance where needed while avoiding leakage current in the contact region.
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 suppresses voltage drops and leakage currents, ensuring uniform brightness across large-sized OLED devices by enabling easy contact between cathode and auxiliary electrodes and optimizing the organic emission layer's non-disposition areas.
Implementation Method 1
an emission layer is formed between two different electrodes, and when electrons generated from one of the electrodes and holes generated from the other one electrode are injected into the emission layer, the injected electrons and holes are combined into excitons. When the generated excitons transfer from an excited state to a ground state, lights are emitted
Data Source
AI summary
An organic light emitting display device can include a substrate; a first electrode and an auxiliary electrode disposed on the substrate; a bank pattern disposed on a part of an upper surface of the first electrode and the auxiliary electrode, in which the bank pattern is divided into a first area and a second area disposed under the first area; a barrier rib disposed on a part of the upper surface of the auxiliary electrode, in which the barrier rib is divided into a third area having a reverse-tapered shape and a fourth area disposed under the third area and having a tapered shape; an organic emission layer disposed on the substrate; and a second electrode disposed on the organic emission layer.