Bankless OLED Pixel Structure for Light Leakage And Short-Circuit Control
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Solution Overview
Problem
Conventional organic light-emitting diode (OLED) display devices require a bank layer for defining emission areas, which increases manufacturing complexity and cost, and can lead to short circuits and light leakage due to the absence of a bankless structure.
Innovation Solution
A bankless display device structure is implemented, where a via hole is formed in the overcoat layer or passivation layer, and a light absorption layer is used in the non-emission area to prevent light emission and short circuits, with a repair pattern to maintain pixel functionality without damaging the light-emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bank layer is used to define emission areas, then light leakage and short circuits are prevented, but manufacturing complexity and cost increase
Solution Approach 1:
The patent removes the bank layer from the OLED structure entirely, extracting this component that caused manufacturing complexity. Instead of using a bank layer to define emission areas, the invention uses the emission layer itself and its surrounding structures to achieve the same function, thereby simplifying the manufacturing process while maintaining reliability
Solution Approach 2:
The emission layer and surrounding structures are made to serve multiple functions: they define the emission area, prevent light leakage, and prevent short circuits between anode and cathode. This multi-functionality replaces the need for a separate bank layer, reducing device complexity while maintaining the protective functions
2Reliability
If a bank layer is used to define emission areas, then light leakage is prevented, but manufacturing cost increases
Solution Approach 1:
The bank layer is extracted from the structure, eliminating the additional manufacturing steps and materials required for its deposition and patterning. The emission layer and surrounding structures assume the light leakage prevention function, reducing overall manufacturing cost
Solution Approach 2:
The functions of the bank layer (defining emission area and preventing light leakage) are merged into the emission layer and surrounding structures. This consolidation reduces the number of separate manufacturing processes required, thereby lowering manufacturing cost
3Productivity
If a bankless structure is implemented, then manufacturing steps are reduced, but risk of short circuits increases
Solution Approach 1:
The emission layer is designed with different properties in different regions: within the emission area it allows light emission, while in surrounding areas it serves as an insulator to prevent short circuits. This local differentiation of material properties maintains reliability without requiring a bank layer
Solution Approach 2:
The emission layer acts as an intermediary structure that simultaneously defines the emission area and provides electrical insulation. This intermediate function prevents direct contact between anode and cathode in non-emission areas, reducing short circuit risk while maintaining manufacturing efficiency
4Ease of manufacture
If a bankless structure is implemented, then manufacturing cost is reduced, but light emission control becomes more difficult
Solution Approach 1:
The emission layer is engineered with spatially varying characteristics: in the emission area it has properties that allow efficient light emission, while in surrounding areas it has properties that prevent light leakage. This local quality control achieves precise light emission control without increasing manufacturing cost
Data Source
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AI summary
a display device having a bankless structure may comprises: a substrate on which pixels including an emission area and a non-emission area are disposed; a first conductive layer disposed on the substrate, and including a lower electrode of a storage capacitor; an active layer formed on the first conductive layer; a second conductive layer formed on the active layer, and including electrodes of at least one transistor, and an upper electrode of the storage capacitor which is formed in a single pattern with at least one of the electrodes of the at least one transistor; an overcoat layer covering the second conductive layer; and a light-emitting element may be disposed on the overcoat layer, and connected to the upper electrode of the storage capacitor through a via hole, wherein the via hole does not overlap the at least one transistor, when viewed from above.