Organic Light-Emitting Display Buffer Layer with Varying Refractive Index
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Solution Overview
Problem
Existing organic light-emitting display devices face challenges in achieving excellent optical and device characteristics, particularly in color reproduction and electrical stability, due to defects in polysilicon active layers and inadequate hydrogen distribution in insulating layers.
Innovation Solution
The implementation of a buffer layer with insulating layers of different refractive indexes, where the uppermost layer has a reduced hydrogen content and is thicker, and the layer under it is filled with silicon nitride to cure defects, along with a gate insulating layer with varying hydrogen content and materials, enhances the electrical properties and color reproduction range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer buffer layer is used, then the manufacturing process is simple, but the color reproduction range and electrical stability are insufficient
Solution Approach 1:
The buffer layer is divided into multiple insulating layers with different refractive indexes (first insulating layer with refractive index 1.4-1.6, second insulating layer with refractive index 1.8-2.0). This segmentation allows each layer to contribute differently to optical resonance and electrical stability, resolving the contradiction between manufacturing simplicity and device reliability
Solution Approach 2:
The patent uses composite insulating layers made of different materials (e.g., silicon oxide for the first layer, silicon nitride for the second layer) with distinct refractive indexes. This composite structure enhances both color reproduction range through optical resonance and electrical stability through defect curing, while maintaining compatibility with existing manufacturing processes
2Ease of manufacture
If the buffer layer has uniform thickness, then the manufacturing process is simple, but the optical resonance effect and color reproduction are insufficient
Solution Approach 1:
The buffer layer is designed with non-uniform thickness where the first insulating layer has a first thickness and the second insulating layer has a second thickness greater than the first. This local variation in thickness optimizes optical resonance for different wavelengths, expanding the color reproduction range while using standard deposition processes
Solution Approach 2:
The patent introduces thickness variation in the vertical dimension of the buffer layer structure. By controlling the thickness of each insulating layer differently, the optical path length varies, creating enhanced optical resonance effects that improve color reproduction without complicating the horizontal manufacturing process
3Reliability
If hydrogen-rich insulating layers are used, then defect sites in polysilicon are cured, but electrical stability deteriorates due to hydrogen outgassing
Solution Approach 1:
The insulating layers are segmented with the hydrogen-rich second layer (silicon nitride) positioned away from the active layer, and the first layer (silicon oxide) positioned adjacent to it. This segmentation isolates the hydrogen source from the active layer while maintaining defect curing functionality, preventing hydrogen outgassing from degrading electrical stability
Solution Approach 2:
The first insulating layer acts as an intermediary barrier between the hydrogen-rich second layer and the active layer. It allows the second layer to cure defects in the polysilicon active layer while preventing hydrogen atoms from migrating to and outgassing from the active layer, thus maintaining electrical stability
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
This configuration improves the color reproduction range and electrical stability of the organic light-emitting display device by minimizing defect sites in polysilicon and optimizing the refractive index structure, resulting in a more efficient resonance effect and simplified manufacturing process.
Implementation Method 1
a buffer layer disposed on a substrate and including a plurality of insulating layers having different refractive indexes
Implementation Method 2
The optical resonance structure may vary an optical length of each wavelength of light emitted from an organic emission layer of each different pixel
Data Source
AI summary
An organic light-emitting display device includes a buffer layer on a substrate that has a plurality of insulating layers having different refractive indexes, and at least one of the insulating layers have different thicknesses on the same level. The device further includes an active layer of a thin film transistor in a thick area of the buffer layer, a pixel electrode in a thin area of the buffer layer, a gate electrode of the thin film transistor on the active layer and source and drain electrodes of the thin film transistor connected to the active layer, and a gate insulating layer between the gate electrode and the source and drain electrodes. The device also includes an emission layer on the pixel electrode, an opposite electrode facing the pixel electrode, and the emission layer is between the opposite electrode and the pixel electrode.