Pixel Circuit Repair Capacitors for OLED Dark Point Defects
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Solution Overview
Problem
Display devices, particularly organic light-emitting display devices, suffer from defects such as dark point defects due to short circuits between anode and cathode electrodes, which are often undetectable and lead to poor quality issues and reduced production yield.
Innovation Solution
A pixel circuit design incorporating first and second light-emitting elements, a driving element, connection lines, and parallel repair capacitors, along with a repair wire and additional gate layer, allows for secondary repair processes even when primary repairs fail, ensuring normal pixel operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit structure is used, then the manufacturing process is simple, but undetectable defects such as short circuits between anode and cathode electrodes occur, leading to dark point defects and reduced production yield
Solution Approach 1:
The anode electrode is divided into first and second anode electrodes, and the light-emitting element is divided into first and second light-emitting elements. This segmentation allows independent repair of each segment, enabling the system to maintain functionality even when one segment is defective, thus improving reliability without requiring complete system replacement
Solution Approach 2:
Repair capacitors are pre-connected in parallel to the connection lines before the defect occurs. When a short circuit is detected, the repair capacitors can immediately be activated to bypass the defective segment, enabling rapid repair without requiring complex real-time decision-making or system reconfiguration
Solution Approach 3:
A driving element is introduced as an intermediary component that can selectively drive different light-emitting elements. When a defect is detected in one path, the driving element can switch to drive the other path, thereby mediating the system's response to defects and maintaining overall functionality
2Productivity
If primary repair process is used, then the repair process is simple, but undetectable defects cannot be reliably repaired, resulting in failed repairs and reduced production yield
Solution Approach 1:
The pixel circuit is segmented into multiple independent paths with separate anode electrodes and light-emitting elements. This segmentation enables the system to perform multiple repair attempts by isolating and replacing individual segments, thereby increasing the probability of successful repair for undetectable defects
Solution Approach 2:
The parallel connection of repair capacitors to connection lines is established in advance during manufacturing. When defects occur, these pre-positioned capacitors can be immediately activated to provide alternative current paths, enabling rapid secondary repair without requiring additional manufacturing steps or complex repair procedures
Solution Approach 3:
The patent enables the discarding of defective segments (such as faulty anode electrodes or light-emitting elements) and the recovery of functional segments. By selectively replacing only the defective portions rather than the entire pixel circuit, the system improves production yield while minimizing material waste and repair complexity
Data Source
AI summary
A pixel circuit according to an embodiment and a display device including the same are discussed. The pixel circuit in one example includes a first light-emitting element, a second light-emitting element, a driving element configured to drive the first and second light-emitting elements, a first connection line connected between a source node of the driving element and a first anode electrode of the first light-emitting element, a second connection line connected between the source node of the driving element and a second anode electrode of the second light-emitting element, a first repair capacitor connected in parallel to the first connection line, and a second repair capacitor connected in parallel to the second connection line.