Passivation Layer Edge Coverage for OLED Moisture Protection
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Solution Overview
Problem
Organic light emitting displays are prone to deterioration due to moisture and oxygen penetration through the interface between the planarization layer and the substrate, leading to hydrogen generation and oxide layer formation, which can shield current flow and lift the cathode, causing functional failures.
Innovation Solution
A passivation layer is formed to cover the edge portion of the planarization layer, comprising silicon nitride or silicon oxide, with a length ranging from 50 μm to 500 μm, and a sealant is applied between the substrate and cover substrate to prevent moisture and oxygen ingress, using materials like ITO, IZO, or ZnO for electrodes and Mg, Ag, or Al for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the planarization layer is positioned on the thin film transistor without additional protective layers, then the manufacturing process is simple, but moisture and oxygen penetrate through the interface between the planarization layer and substrate, causing deterioration of the organic light emitting display
Solution Approach 1:
The protective structure is divided into multiple segments: the planarization layer (first protective layer), the passivation layer (second protective layer), and the sealant layer (third protective layer). Each layer serves a specific function in preventing moisture and oxygen penetration, with the passivation layer specifically covering the vulnerable interface between the planarization layer and substrate.
Solution Approach 2:
The passivation layer acts as an intermediary protective layer positioned between the planarization layer and the substrate, specifically covering the interface region. This intermediary layer prevents direct contact between moisture/oxygen and the critical interface, blocking the penetration path without interfering with the underlying transistor structure.
2Reliability
If the passivation layer covers the edge portion of the planarization layer, then moisture and oxygen penetration is prevented, but the device structure becomes more complex
Solution Approach 1:
The passivation layer is selectively positioned to cover only the edge portion of the planarization layer where the interface with the substrate is located. This localized protection approach applies the protective function precisely where it is most needed (at the vulnerable interface edge) without unnecessarily complicating the entire device structure.
Solution Approach 2:
The passivation layer extends slightly beyond the edge of the planarization layer to ensure complete coverage of the interface region. This partial extension provides excessive protection at the critical interface area, ensuring that moisture and oxygen penetration is fully blocked even with manufacturing tolerances, without requiring complete coverage of the entire planarization layer.
3Reliability
If sealant is applied between substrate and cover substrate, then moisture and oxygen ingress is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The passivation layer is formed on the substrate before the sealant is applied and before the cover substrate is attached. This preliminary protective layer is in place beforehand to prevent moisture and oxygen ingress at the interface region, providing a pre-established barrier that reduces the precision requirements for subsequent sealant application and assembly processes.
Data Source
AI summary
An organic light emitting display is disclosed. The organic light emitting display includes a substrate, a thin film transistor positioned on the substrate, a planarization layer positioned on the thin film transistor, an emission unit, and a passivation layer. The emission unit is positioned on the planarization layer and electrically connected to the thin film transistor. The passivation layer is positioned on the substrate to cover an edge portion of the planarization layer.